Sample records for ice mass density

  1. Mass balance of the Antarctic ice sheet.

    PubMed

    Wingham, D J; Shepherd, A; Muir, A; Marshall, G J

    2006-07-15

    The Antarctic contribution to sea-level rise has long been uncertain. While regional variability in ice dynamics has been revealed, a picture of mass changes throughout the continental ice sheet is lacking. Here, we use satellite radar altimetry to measure the elevation change of 72% of the grounded ice sheet during the period 1992-2003. Depending on the density of the snow giving rise to the observed elevation fluctuations, the ice sheet mass trend falls in the range -5-+85Gtyr-1. We find that data from climate model reanalyses are not able to characterise the contemporary snowfall fluctuation with useful accuracy and our best estimate of the overall mass trend-growth of 27+/-29Gtyr-1-is based on an assessment of the expected snowfall variability. Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica. The result exacerbates the difficulty of explaining twentieth century sea-level rise.

  2. Modeling of Firn Compaction for Estimating Ice-Sheet Mass Change from Observed Ice-Sheet Elevation Change

    NASA Technical Reports Server (NTRS)

    Li, Jun; Zwally, H. Jay

    2011-01-01

    Changes in ice-sheet surface elevation are caused by a combination of ice-dynamic imbalance, ablation, temporal variations in accumulation rate, firn compaction and underlying bedrock motion. Thus, deriving the rate of ice-sheet mass change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion, which do not involve changes in mass, and requires an appropriate firn density to associate with elevation changes induced by recent accumulation rate variability. We use a 25 year record of surface temperature and a parameterization for accumulation change as a function of temperature to drive a firn compaction model. We apply this formulation to ICESat measurements of surface elevation change at three locations on the Greenland ice sheet in order to separate the accumulation-driven changes from the ice-dynamic/ablation-driven changes, and thus to derive the corresponding mass change. Our calculated densities for the accumulation-driven changes range from 410 to 610 kg/cu m, which along with 900 kg/cu m for the dynamic/ablation-driven changes gives average densities ranging from 680 to 790 kg/cu m. We show that using an average (or "effective") density to convert elevation change to mass change is not valid where the accumulation and the dynamic elevation changes are of opposite sign.

  3. Constraining variable density of ice shelves using wide-angle radar measurements

    NASA Astrophysics Data System (ADS)

    Drews, Reinhard; Brown, Joel; Matsuoka, Kenichi; Witrant, Emmanuel; Philippe, Morgane; Hubbard, Bryn; Pattyn, Frank

    2016-04-01

    The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium, for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g., temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar data sets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. We reconstruct depth to internal reflectors, local ice thickness, and firn-air content using a novel algorithm that includes traveltime inversion and ray tracing with a prescribed shape of the depth-density relationship. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggest that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals that the firn inside the channel is 4.7 % denser than that outside the channel. Hydrostatic ice thickness calculations used for determining basal melt rates should account for the denser firn in ice-shelf channels. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.

  4. Meltwater storage in low-density near-surface bare ice in the Greenland ice sheet ablation zone

    NASA Astrophysics Data System (ADS)

    Cooper, Matthew G.; Smith, Laurence C.; Rennermalm, Asa K.; Miège, Clément; Pitcher, Lincoln H.; Ryan, Jonathan C.; Yang, Kang; Cooley, Sarah W.

    2018-03-01

    We document the density and hydrologic properties of bare, ablating ice in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment in the Kangerlussuaq sector of the western Greenland ice sheet. We find low-density (0.43-0.91 g cm-3, μ = 0.69 g cm-3) ice to at least 1.1 m depth below the ice sheet surface. This near-surface, low-density ice consists of alternating layers of water-saturated, porous ice and clear solid ice lenses, overlain by a thin (< 0.5 m), even lower density (0.33-0.56 g cm-3, μ = 0.45 g cm-3) unsaturated weathering crust. Ice density data from 10 shallow (0.9-1.1 m) ice cores along an 800 m transect suggest an average 14-18 cm of specific meltwater storage within this low-density ice. Water saturation of this ice is confirmed through measurable water levels (1-29 cm above hole bottoms, μ = 10 cm) in 84 % of cryoconite holes and rapid refilling of 83 % of 1 m drilled holes sampled along the transect. These findings are consistent with descriptions of shallow, depth-limited aquifers on the weathered surface of glaciers worldwide and confirm the potential for substantial transient meltwater storage within porous low-density ice on the Greenland ice sheet ablation zone surface. A conservative estimate for the ˜ 63 km2 supraglacial catchment yields 0.009-0.012 km3 of liquid meltwater storage in near-surface, porous ice. Further work is required to determine if these findings are representative of broader areas of the Greenland ice sheet ablation zone, and to assess the implications for sub-seasonal mass balance processes, surface lowering observations from airborne and satellite altimetry, and supraglacial runoff processes.

  5. Surface and basal ice shelf mass balance processes of the Southern McMurdo Ice Shelf determined through radar statistical reconnaissance

    NASA Astrophysics Data System (ADS)

    Grima, C.; Koch, I.; Greenbaum, J. S.; Soderlund, K. M.; Blankenship, D. D.; Young, D. A.; Fitzsimons, S.

    2017-12-01

    The McMurdo ice shelves (northern and southern MIS), adjacent to the eponymous station and the Ross Ice Shelf, Antarctica, are known for large gradients in surface snow accumulation and snow/ice impurities. Marine ice accretion and melting are important contributors to MIS's mass balance. Due to erosive winds, the southern MIS (SMIS) shows a locally negative surface mass balance. Thus, marine ice once accreted at the ice shelf base crops out at the surface. However, the exact processes that exert primary control on SMIS mass balance have remained elusive. Radar statistical reconnaissance (RSR) is a recent technique that has been used to characterize the surface properties of the Earth's cryosphere, Mars, and Titan from the stochastic character of energy scattered by the surface. Here, we apply RSR to map the surface density and roughness of the SMIS and extend the technique to derive the basal reflectance and scattering coefficients of the ice-ocean interface. We use an airborne radar survey grid acquired over the SMIS in the 2014-2015 austral summer by the University of Texas Institute for Geophysics with the High Capability Radar Sounder (HiCARS2; 60-MHz center frequency and 15-MHz bandwidth). The RSR-derived snow density values and patterns agree with directly -measured ice shelf surface accumulation rates. We also compare the composition of SMIS ice surface samples to test the ability of RSR to discriminate ices with varying dielectric properties (e.g., marine versus meteoric ice) and hypothesize relationships between the RSR-derived basal reflectance/scattered coefficients and accretion or melting at the ice-ocean interface. This improved knowledge of air-ice and ice-ocean boundaries provides a new perspective on the processes governing SMIS surface and basal mass balance.

  6. Effective Ice Particle Densities for Cold Anvil Cirrus

    NASA Technical Reports Server (NTRS)

    Heymsfield, Andrew J.; Schmitt, Carl G.; Bansemer, Aaron; Baumgardner, Darrel; Weinstock, Elliot M.; Smith, Jessica

    2002-01-01

    This study derives effective ice particle densities from data collected from the NASA WB-57F aircraft near the tops of anvils during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in southern Florida in July 2002. The effective density, defined as the ice particle mass divided by the volume of an equivalent diameter liquid sphere, is obtained for particle populations and single sizes containing mixed particle habits using measurements of condensed water content and particle size distributions. The mean effective densities for populations decrease with increasing slopes of the gamma size distributions fitted to the size distributions. The population-mean densities range from near 0.91 g/cu m to 0.15 g/cu m. Effective densities for single sizes obey a power-law with an exponent of about -0.55, somewhat less steep than found from earlier studies. Our interpretations apply to samples where particle sizes are generally below 200-300 microns in maximum dimension because of probe limitations.

  7. Antarctic Ice Mass Balance from GRACE

    NASA Astrophysics Data System (ADS)

    Boening, C.; Firing, Y. L.; Wiese, D. N.; Watkins, M. M.; Schlegel, N.; Larour, E. Y.

    2014-12-01

    The Antarctic ice mass balance and rates of change of ice mass over the past decade are analyzed based on observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, in the form of JPL RL05M mascon solutions. Surface mass balance (SMB) fluxes from ERA-Interim and other atmospheric reanalyses successfully account for the seasonal GRACE-measured mass variability, and explain 70-80% of the continent-wide mass variance at interannual time scales. Trends in the residual (GRACE mass - SMB accumulation) mass time series in different Antarctic drainage basins are consistent with time-mean ice discharge rates based on radar-derived ice velocities and thicknesses. GRACE also resolves accelerations in regional ice mass change rates, including increasing rates of mass gain in East Antarctica and accelerating ice mass loss in West Antarctica. The observed East Antarctic mass gain is only partially explained by anomalously large SMB events in the second half of the record, potentially implying that ice discharge rates are also decreasing in this region. Most of the increasing mass loss rate in West Antarctica, meanwhile, is explained by decreasing SMB (principally precipitation) over this time period, part of the characteristic decadal variability in regional SMB. The residual acceleration of 2+/-1 Gt/yr, which is concentrated in the Amundsen Sea Embayment (ASE) basins, represents the contribution from increasing ice discharge rates. An Ice Sheet System Model (ISSM) run with constant ocean forcing and stationary grounding lines both underpredicts the largest trends in the ASE and produces negligible acceleration or interannual variability in discharge, highlighting the potential importance of ocean forcing for setting ice discharge rates at interannual to decadal time scales.

  8. The mass balance of the ice plain of Ice Stream B and Crary Ice Rise

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert

    1993-01-01

    The region in the mouth of Ice Stream B (the ice plain) and that in the vicinity of Crary Ice Rise are experiencing large and rapid changes. Based on velocity, ice thickness, and accumulation rate data, the patterns of net mass balance in these regions were calculated. Net mass balance, or the rate of ice thickness change, was calculated as the residual of all mass fluxes into and out of subregions (or boxes). Net mass balance provides a measure of the state of health of the ice sheet and clues to the current dynamics.

  9. Inter-annual Variations in Snow/Firn Density over the Greenland Ice Sheet by Combining GRACE gravimetry and Envisat Altimetry

    NASA Astrophysics Data System (ADS)

    Su, X.; Shum, C. K.; Guo, J.; Howat, I.; Jezek, K. C.; Luo, Z.; Zhou, Z.

    2017-12-01

    Satellite altimetry has been used to monitor elevation and volume change of polar ice sheets since the 1990s. In order to derive mass change from the measured volume change, different density assumptions are commonly used in the research community, which may cause discrepancies on accurately estimating ice sheets mass balance. In this study, we investigate the inter-annual anomalies of mass change from GRACE gravimetry and elevation change from Envisat altimetry during years 2003-2009, with the objective of determining inter-annual variations of snow/firn density over the Greenland ice sheet (GrIS). High positive correlations (0.6 or higher) between these two inter-annual anomalies at are found over 93% of the GrIS, which suggests that both techniques detect the same geophysical process at the inter-annual timescale. Interpreting the two anomalies in terms of near surface density variations, over 80% of the GrIS, the inter-annual variation in average density is between the densities of snow and pure ice. In particular, at the Summit of Central Greenland, we validate the satellite data estimated density with the in situ data available from 75 snow pits and 9 ice cores. This study provides constraints on the currently applied density assumptions for the GrIS.

  10. Autonomous Ice Mass Balance Buoys for Seasonal Sea Ice

    NASA Astrophysics Data System (ADS)

    Whitlock, J. D.; Planck, C.; Perovich, D. K.; Parno, J. T.; Elder, B. C.; Richter-Menge, J.; Polashenski, C. M.

    2017-12-01

    The ice mass-balance represents the integration of all surface and ocean heat fluxes and attributing the impact of these forcing fluxes on the ice cover can be accomplished by increasing temporal and spatial measurements. Mass balance information can be used to understand the ongoing changes in the Arctic sea ice cover and to improve predictions of future ice conditions. Thinner seasonal ice in the Arctic necessitates the deployment of Autonomous Ice Mass Balance buoys (IMB's) capable of long-term, in situ data collection in both ice and open ocean. Seasonal IMB's (SIMB's) are free floating IMB's that allow data collection in thick ice, thin ice, during times of transition, and even open water. The newest generation of SIMB aims to increase the number of reliable IMB's in the Arctic by leveraging inexpensive commercial-grade instrumentation when combined with specially developed monitoring hardware. Monitoring tasks are handled by a custom, expandable data logger that provides low-cost flexibility for integrating a large range of instrumentation. The SIMB features ultrasonic sensors for direct measurement of both snow depth and ice thickness and a digital temperature chain (DTC) for temperature measurements every 2cm through both snow and ice. Air temperature and pressure, along with GPS data complete the Arctic picture. Additionally, the new SIMB is more compact to maximize deployment opportunities from multiple types of platforms.

  11. Detecting high spatial variability of ice shelf basal mass balance, Roi Baudouin Ice Shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    Berger, Sophie; Drews, Reinhard; Helm, Veit; Sun, Sainan; Pattyn, Frank

    2017-11-01

    Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB), i.e. the difference between refreezing and melting. Here, we present an improved technique - based on satellite observations - to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmospheric-model surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from -14.7 to 8.6 m a-1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km) lowers by 0.5 to 1.4 m a-1, which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks). However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing) toward the ice shelf front. Although the absolute, satellite-based BMB values remain uncertain, we have

  12. Multi-channel Ice Penetrating Radar Traverse for Estimates of Firn Density in the Percolation Zone, Western Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Meehan, T.; Osterberg, E. C.; Lewis, G.; Overly, T. B.; Hawley, R. L.; Bradford, J.; Marshall, H. P.

    2016-12-01

    To better predict the response of the Greenland Ice Sheet (GrIS) to future warming, leading edge Regional Climate Models (RCM) must be calibrated with in situ measurements of recent accumulation and melt. Mass balance estimates averaged across the entire Greenland Ice Sheet (GrIS) vary between models by more than 30 percent, and regional comparisons of mass balance reconstructions in Greenland vary by 100 percent or more. Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) is a multi-year and multi-disciplinary 1700 km science traverse from Raven/Dye2 in SW Greenland, to Summit Station. Multi-offset radar measurements can provide high accuracy electromagnetic (EM) velocity estimates of the firn to within (+-) 0.002 to 0.003 m/ns. EM velocity, in turn, can be used to estimate bulk firn density. Using a mixing equation such as the CRIM Equation we use the measured EM velocity, along with the known EM velocity in air and ice, to estimate bulk density. During spring 2016, we used multi-channel 500MHz radar in a multi-offset configuration to survey more than 800 km from Raven towards summit. Preliminary radar-derived snow density estimates agree with density estimates from a firn core measurement ( 50 kg/m3), despite the lateral heterogeneity of the firn across the length of the antenna array (12 m).

  13. Ice-sheet mass balance and climate change.

    PubMed

    Hanna, Edward; Navarro, Francisco J; Pattyn, Frank; Domingues, Catia M; Fettweis, Xavier; Ivins, Erik R; Nicholls, Robert J; Ritz, Catherine; Smith, Ben; Tulaczyk, Slawek; Whitehouse, Pippa L; Zwally, H Jay

    2013-06-06

    Since the 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report, new observations of ice-sheet mass balance and improved computer simulations of ice-sheet response to continuing climate change have been published. Whereas Greenland is losing ice mass at an increasing pace, current Antarctic ice loss is likely to be less than some recently published estimates. It remains unclear whether East Antarctica has been gaining or losing ice mass over the past 20 years, and uncertainties in ice-mass change for West Antarctica and the Antarctic Peninsula remain large. We discuss the past six years of progress and examine the key problems that remain.

  14. High-density amorphous ice: nucleation of nanosized low-density amorphous ice

    NASA Astrophysics Data System (ADS)

    Tonauer, Christina M.; Seidl-Nigsch, Markus; Loerting, Thomas

    2018-01-01

    The pressure dependence of the crystallization temperature of different forms of expanded high-density amorphous ice (eHDA) was scrutinized. Crystallization at pressures 0.05-0.30 GPa was followed using volumetry and powder x-ray diffraction. eHDA samples were prepared via isothermal decompression of very high-density amorphous ice at 140 K to different end pressures between 0.07-0.30 GPa (eHDA0.07-0.3). At 0.05-0.17 GPa the crystallization line T x (p) of all eHDA variants is the same. At pressures  >0.17 GPa, all eHDA samples decompressed to pressures  <0.20 GPa exhibit significantly lower T x values than eHDA0.2 and eHDA0.3. We rationalize our findings with the presence of nanoscaled low-density amorphous ice (LDA) seeds that nucleate in eHDA when it is decompressed to pressures  <0.20 GPa at 140 K. Below ~0.17 GPa, these nanosized LDA domains are latent within the HDA matrix, exhibiting no effect on T x of eHDA<0.2. Upon heating at pressures  ⩾0.17 GPa, these nanosized LDA nuclei transform to ice IX nuclei. They are favored sites for crystallization and, hence, lower T x . By comparing crystallization experiments of bulk LDA with the ones involving nanosized LDA we are able to estimate the Laplace pressure and radius of ~0.3-0.8 nm for the nanodomains of LDA. The nucleation of LDA in eHDA revealed here is evidence for the first-order-like nature of the HDA  →  LDA transition, supporting water’s liquid-liquid transition scenarios.

  15. Local and Total Density Measurements in Ice Shapes

    NASA Technical Reports Server (NTRS)

    Vargas, Mario; Broughton, Howard; Sims, James J.; Bleeze, Brian; Gaines, Vatanna

    2005-01-01

    Preliminary measurements of local and total densities inside ice shapes were obtained from ice shapes grown in the NASA Glenn Research Tunnel for a range of glaze ice, rime ice, and mixed phase ice conditions on a NACA 0012 airfoil at 0 angle of attack. The ice shapes were removed from the airfoil and a slice of ice 3 mm thick was obtained using a microtome. The resulting samples were then x-rayed to obtain a micro-radiography, the film was digitized, and image processing techniques were used to extract the local and total density values.

  16. Estimating the rates of mass change, ice volume change and snow volume change in Greenland from ICESat and GRACE data

    NASA Astrophysics Data System (ADS)

    Slobbe, D. C.; Ditmar, P.; Lindenbergh, R. C.

    2009-01-01

    The focus of this paper is on the quantification of ongoing mass and volume changes over the Greenland ice sheet. For that purpose, we used elevation changes derived from the Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry mission and monthly variations of the Earth's gravity field as observed by the Gravity Recovery and Climate Experiment (GRACE) mission. Based on a stand alone processing scheme of ICESat data, the most probable estimate of the mass change rate from 2003 February to 2007 April equals -139 +/- 68 Gtonyr-1. Here, we used a density of 600+/-300 kgm-3 to convert the estimated elevation change rate in the region above 2000m into a mass change rate. For the region below 2000m, we used a density of 900+/-300 kgm-3. Based on GRACE gravity models from half 2002 to half 2007 as processed by CNES, CSR, DEOS and GFZ, the estimated mass change rate for the whole of Greenland ranges between -128 and -218Gtonyr-1. Most GRACE solutions show much stronger mass losses as obtained with ICESat, which might be related to a local undersampling of the mass loss by ICESat and uncertainties in the used snow/ice densities. To solve the problem of uncertainties in the snow and ice densities, two independent joint inversion concepts are proposed to profit from both GRACE and ICESat observations simultaneously. The first concept, developed to reduce the uncertainty of the mass change rate, estimates this rate in combination with an effective snow/ice density. However, it turns out that the uncertainties are not reduced, which is probably caused by the unrealistic assumption that the effective density is constant in space and time. The second concept is designed to convert GRACE and ICESat data into two totally new products: variations of ice volume and variations of snow volume separately. Such an approach is expected to lead to new insights in ongoing mass change processes over the Greenland ice sheet. Our results show for different GRACE solutions a snow

  17. High-Density Amorphous Ice, the Frost on Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

    1995-01-01

    Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

  18. The relation between high-density and very-high-density amorphous ice.

    PubMed

    Loerting, Thomas; Salzmann, Christoph G; Winkel, Katrin; Mayer, Erwin

    2006-06-28

    The exact nature of the relationship between high-density (HDA) and very-high-density (VHDA) amorphous ice is unknown at present. Here we review the relation between HDA and VHDA, concentrating on experimental aspects and discuss these with respect to the relation between low-density amorphous ice (LDA) and HDA. On compressing LDA at 125 K up to 1.5 GPa, two distinct density steps are observable in the pressure-density curves which correspond to the LDA --> HDA and HDA --> VHDA conversion. This stepwise formation process LDA --> HDA --> VHDA at 125 K is the first unambiguous observation of a stepwise amorphous-amorphous-amorphous transformation sequence. Density values of amorphous ice obtained in situ between 0.3 and 1.9 GPa on isobaric heating up to the temperatures of crystallization show a pronounced change of slope at ca. 0.8 GPa which could indicate formation of a distinct phase. We infer that the relation between HDA and VHDA is very similar to that between LDA and HDA except for a higher activation barrier between the former. We further discuss the two options of thermodynamic phase transition versus kinetic densification for the HDA --> VHDA conversion.

  19. Infrared Observations of Hot Gas and Cold Ice Toward the Low Mass Protostar Elias 29

    NASA Technical Reports Server (NTRS)

    Boogert, A. C. A.; Tielens, A. G. G. M.; Ceccarelli, C.; Boonman, A. M. S.; vanDishoeck, E. F.; Keane, J. V.; Whittet, D. C. B.; deGraauw, T.

    2000-01-01

    We have obtained the full 1-200 micrometer spectrum of the low luminosity (36 solar luminosity Class I protostar Elias 29 in the rho Ophiuchi molecular cloud. It provides a unique opportunity to study the origin and evolution of interstellar ice and the interrelationship of interstellar ice and hot core gases around low mass protostars. We see abundant hot CO and H2O gas, as well as the absorption bands of CO, CO2, H2O and "6.85 micrometer" ices. We compare the abundances and physical conditions of the gas and ices toward Elias 29 with the conditions around several well studied luminous, high mass protostars. The high gas temperature and gas/solid ratios resemble those of relatively evolved high mass objects (e.g. GL 2591). However, none of the ice band profiles shows evidence for significant thermal processing, and in this respect Elias 29 resembles the least evolved luminous protostars, such as NGC 7538 : IRS9. Thus we conclude that the heating of the envelope of the low mass object Elias 29 is qualitatively different from that of high mass protostars. This is possibly related to a different density gradient of the envelope or shielding of the ices in a circumstellar disk. This result is important for our understanding of the evolution of interstellar ices, and their relation to cometary ices.

  20. Greenland Ice Sheet Mass Balance

    NASA Technical Reports Server (NTRS)

    Reeh, N.

    1984-01-01

    Mass balance equation for glaciers; areal distribution and ice volumes; estimates of actual mass balance; loss by calving of icebergs; hydrological budget for Greenland; and temporal variations of Greenland mass balance are examined.

  1. Earth Structure, Ice Mass Changes, and the Local Dynamic Geoid

    NASA Astrophysics Data System (ADS)

    Harig, C.; Simons, F. J.

    2014-12-01

    Spherical Slepian localization functions are a useful method for studying regional mass changes observed by satellite gravimetry. By projecting data onto a sparse basis set, the local field can be estimated more easily than with the full spherical harmonic basis. We have used this method previously to estimate the ice mass change in Greenland from GRACE data, and it can also be applied to other planetary problems such as global magnetic fields. Earth's static geoid, in contrast to the time-variable field, is in large part related to the internal density and rheological structure of the Earth. Past studies have used dynamic geoid kernels to relate this density structure and the internal deformation it induces to the surface geopotential at large scales. These now classical studies of the eighties and nineties were able to estimate the mantle's radial rheological profile, placing constraints on the ratio between upper and lower mantle viscosity. By combining these two methods, spherical Slepian localization and dynamic geoid kernels, we have created local dynamic geoid kernels which are sensitive only to density variations within an area of interest. With these kernels we can estimate the approximate local radial rheological structure that best explains the locally observed geoid on a regional basis. First-order differences of the regional mantle viscosity structure are accessible to this technique. In this contribution we present our latest, as yet unpublished results on the geographical and temporal pattern of ice mass changes in Antarctica over the past decade, and we introduce a new approach to extract regional information about the internal structure of the Earth from the static global gravity field. Both sets of results are linked in terms of the relevant physics, but also in being developed from the marriage of Slepian functions and geoid kernels. We make predictions on the utility of our approach to derive fully three-dimensional rheological Earth models, to

  2. Greenland ice sheet mass balance: a review.

    PubMed

    Khan, Shfaqat A; Aschwanden, Andy; Bjørk, Anders A; Wahr, John; Kjeldsen, Kristian K; Kjær, Kurt H

    2015-04-01

    Over the past quarter of a century the Arctic has warmed more than any other region on Earth, causing a profound impact on the Greenland ice sheet (GrIS) and its contribution to the rise in global sea level. The loss of ice can be partitioned into processes related to surface mass balance and to ice discharge, which are forced by internal or external (atmospheric/oceanic/basal) fluctuations. Regardless of the measurement method, observations over the last two decades show an increase in ice loss rate, associated with speeding up of glaciers and enhanced melting. However, both ice discharge and melt-induced mass losses exhibit rapid short-term fluctuations that, when extrapolated into the future, could yield erroneous long-term trends. In this paper we review the GrIS mass loss over more than a century by combining satellite altimetry, airborne altimetry, interferometry, aerial photographs and gravimetry data sets together with modelling studies. We revisit the mass loss of different sectors and show that they manifest quite different sensitivities to atmospheric and oceanic forcing. In addition, we discuss recent progress in constructing coupled ice-ocean-atmosphere models required to project realistic future sea-level changes.

  3. Airborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice density

    NASA Astrophysics Data System (ADS)

    Rack, Wolfgang; Haas, Christian; Langhorne, Pat J.

    2013-11-01

    We present airborne measurements to investigate the thickness of the western McMurdo Ice Shelf in the western Ross Sea, Antarctica. Because of basal accretion of marine ice and brine intrusions conventional radar systems are limited in detecting the ice thickness in this area. In November 2009, we used a helicopter-borne laser and electromagnetic induction sounder (EM bird) to measure several thickness and freeboard profiles across the ice shelf. The maximum electromagnetically detectable ice thickness was about 55 m. Assuming hydrostatic equilibrium, the simultaneous measurement of ice freeboard and thickness was used to derive bulk ice densities ranging from 800 to 975 kg m-3. Densities higher than those of pure ice can be largely explained by the abundance of sediments accumulated at the surface and present within the ice shelf, and are likely to a smaller extent related to the overestimation of ice thickness by the electromagnetic induction measurement related to the presence of a subice platelet layer. The equivalent thickness of debris at a density of 2800 kg m-3 is found to be up to about 2 m thick. A subice platelet layer below the ice shelf, similar to what is observed in front of the ice shelf below the sea ice, is likely to exist in areas of highest thickness. The thickness and density distribution reflects a picture of areas of basal freezing and supercooled Ice Shelf Water emerging from below the central ice shelf cavity into McMurdo Sound.

  4. Changes in ice dynamics and mass balance of the Antarctic ice sheet.

    PubMed

    Rignot, Eric

    2006-07-15

    The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 degrees C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.

  5. Ice Mass Fluctuations and Earthquake Hazard

    NASA Technical Reports Server (NTRS)

    Sauber, J.

    2006-01-01

    In south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing ice wastage over the last 100-150 years [Sauber et al., 2000; Sauber and Molnia, 2004]. In this study we focus on the region referred to as the Yakataga segment of the Pacific-North American plate boundary zone in Alaska. In this region, the Bering and Malaspina glacier ablation zones have average ice elevation decreases from 1-3 meters/year (see summary and references in Molnia, 2005). The elastic response of the solid Earth to this ice mass decrease alone would cause several mm/yr of horizontal motion and uplift rates of up to 10-12 mm/yr. In this same region observed horizontal rates of tectonic deformation range from 10 to 40 mm/yr to the north-northwest and the predicted tectonic uplift rates range from -2 mm/year near the Gulf of Alaska coast to 12mm/year further inland [Savage and Lisowski, 1988; Ma et al, 1990; Sauber et al., 1997, 2000, 2004; Elliot et al., 2005]. The large ice mass changes associated with glacial wastage and surges perturb the tectonic rate of deformation at a variety of temporal and spatial scales. The associated incremental stress change may enhance or inhibit earthquake occurrence. We report recent (seasonal to decadal) ice elevation changes derived from data from NASA's ICESat satellite laser altimeter combined with earlier DEM's as a reference surface to illustrate the characteristics of short-term ice elevation changes [Sauber et al., 2005, Muskett et al., 2005]. Since we are interested in evaluating the effect of ice changes on faulting potential, we calculated the predicted surface displacement changes and incremental stresses over a specified time interval and calculated the change in the fault stability margin using the approach given by Wu and Hasegawa [1996]. Additionally, we explored the possibility that these ice mass fluctuations altered the seismic rate of background seismicity. Although we primarily focus on

  6. Improving Surface Mass Balance Over Ice Sheets and Snow Depth on Sea Ice

    NASA Technical Reports Server (NTRS)

    Koenig, Lora Suzanne; Box, Jason; Kurtz, Nathan

    2013-01-01

    Surface mass balance (SMB) over ice sheets and snow on sea ice (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists' abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On ice sheets, snow accumulation is the sole mass gain to SMB, and meltwater runoff can be the dominant single loss factor in extremely warm years such as 2012. SOSI affects the growth and melt cycle of the Earth's polar sea ice cover. The summer of 2012 saw the largest satellite-recorded melt area over the Greenland ice sheet and the smallest satellite-recorded Arctic sea ice extent, making this meeting both timely and relevant.

  7. The Ice Sheet Mass Balance Inter-comparison Exercise

    NASA Astrophysics Data System (ADS)

    Shepherd, A.; Ivins, E. R.

    2015-12-01

    Fluctuations in the mass of ice stored in Antarctica and Greenland are of considerable societal importance. The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a joint-initiative of ESA and NASA aimed at producing a single estimate of the global sea level contribution to polar ice sheet losses. Within IMBIE, estimates of ice sheet mass balance are developed from a variety of satellite geodetic techniques using a common spatial and temporal reference frame and a common appreciation of the contributions due to external signals. The project brings together the laboratories and space agencies that have been instrumental in developing independent estimates of ice sheet mass balance to date. In its first phase, IMBIE involved 27 science teams, and delivered a first community assessment of ice sheet mass imbalance to replace 40 individual estimates. The project established that (i) there is good agreement between the three main satellite-based techniques for estimating ice sheet mass balance, (ii) combining satellite data sets leads to significant improvement in certainty, (iii) the polar ice sheets contributed 11 ± 4 mm to global sea levels between 1992 and 2012, and (iv) that combined ice losses from Antarctica and Greenland have increased over time, rising from 10% of the global trend in the early 1990's to 30% in the late 2000's. Demand for an updated assessment has grown, and there are now new satellite missions, new geophysical corrections, new techniques, and new teams producing data. The period of overlap between independent satellite techniques has increased from 5 to 12 years, and the full period of satellite data over which an assessment can be performed has increased from 19 to 40 years. It is also clear that multiple satellite techniques are required to confidently separate mass changes associated with snowfall and ice dynamical imbalance - information that is of critical importance for climate modelling. This presentation outlines the approach

  8. Reconciling different observations of the CO2 ice mass loading of the Martian north polar cap

    USGS Publications Warehouse

    Haberle, R.M.; Mattingly, B.; Titus, T.N.

    2004-01-01

    The GRS measurements of the peak mass loading of the north polar CO2 ice cap on Mars are about 60% lower than those calculated from MGS TES radiation data and those inferred from the MOLA cap thicknesses. However, the GRS data provide the most accurate measurement of the mass loading. We show that the TES and MOLA data can be reconciled with the GRS data if (1) subsurface heat conduction and atmospheric heat transport are included in the TES mass budget calculations, and (2) the density of the polar deposits is ???600 kg m-3. The latter is much less than that expected for slab ice (???1600 kg m-3) and suggests that processes unique to the north polar region are responsible for the low cap density. Copyright 2004 by the American Geophysical Union.

  9. High Artic Glaciers and Ice Caps Ice Mass Change from GRACE, Regional Climate Model Output and Altimetry.

    NASA Astrophysics Data System (ADS)

    Ciraci, E.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.

    2016-12-01

    The Arctic hosts more than the 75% of the ice covered regions outside from Greenland and Antarctica. Available observations show that increased atmospheric temperatures during the last century have contributed to a substantial glaciers retreat in all these regions. We use satellite gravimetry by the NASA's Gravity Recovery and Climate Experiment (GRACE), and apply a least square fit mascon approach to calculate time series of ice mass change for the period 2002-2016. Our estimates show that arctic glaciers have constantly contributed to the sea level rise during the entire observation period with a mass change of -170+/-20 Gt/yr equivalent to the 80% of the total ice mass change from the world Glacier and Ice Caps (GIC) excluding the Ice sheet peripheral GIC, which we calculated to be -215+/-32 GT/yr, with an acceleration of 9+/-4 Gt/yr2. The Canadian Archipelago is the main contributor to the total mass depletion with an ice mass trend of -73+/-9 Gt/yr and a significant acceleration of -7+/-3 Gt/yr2. The increasing mass loss is mainly determined by melting glaciers located in the northern part of the archipelago.In order to investigate the physical processes driving the observed ice mass loss we employ satellite altimetry and surface mass balance (SMB) estimates from Regional climate model outputs available for the same time period covered by the gravimetry data. We use elevation data from the NASA ICESat (2003-2009) and ESA CryoSat-2 (2010-2016) missions to estimate ice elevation changes. We compare GRACE ice mass estimates with time series of surface mass balance from the Regional Climate Model (RACMO-2) and the Modèle Atmosphérique Régional (MAR) and determine the portion of the total mass change explained by the SMB signal. We find that in Iceland and in the and the Canadian Archipelago the SMB signal explains most of the observed mass changes, suggesting that ice discharge may play a secondary role here. In other region, e.g. in Svalbar, the SMB signal

  10. Measurements of sea ice mass redistribution during ice deformation event in Arctic winter

    NASA Astrophysics Data System (ADS)

    Itkin, P.; Spreen, G.; King, J.; Rösel, A.; Skourup, H.; Munk Hvidegaard, S.; Wilkinson, J.; Oikkonen, A.; Granskog, M. A.; Gerland, S.

    2016-12-01

    Sea-ice growth during high winter is governed by ice dynamics. The highest growth rates are found in leads that open under divergent conditions, where exposure to the cold atmosphere promotes thermodynamic growth. Additionally ice thickens dynamically, where convergence causes rafting and ridging. We present a local study of sea-ice growth and mass redistribution between two consecutive airborne measurements, on 19 and 24 April 2015, during the N-ICE2015 expedition in the area north of Svalbard. Between the two overflights an ice deformation event was observed. Airborne laser scanner (ALS) measurements revisited the same sea-ice area of approximately 3x3 km. By identifying the sea surface within the ALS measurements as a reference the sea ice plus snow freeboard was obtained with a spatial resolution of 5 m. By assuming isostatic equilibrium of level floes, the freeboard heights can be converted to ice thickness. The snow depth is estimated from in-situ measurements. Sea ice thickness measurements were made in the same area as the ALS measurements by electromagnetic sounding from a helicopter (HEM), and with a ground-based device (EM31), which allows for cross-validation of the sea-ice thickness estimated from all 3 procedures. Comparison of the ALS snow freeboard distributions between the first and second overflight shows a decrease in the thin ice classes and an increase of the thick ice classes. While there was no observable snowfall and a very low sea-ice growth of older level ice during this period, an autonomous buoy array deployed in the surroundings of the area measured by the ALS shows first divergence followed by convergence associated with shear. To quantify and link the sea ice deformation with the associated sea-ice thickness change and mass redistribution we identify over 100 virtual buoys in the ALS data from both overflights. We triangulate the area between the buoys and calculate the strain rates and freeboard change for each individual triangle

  11. Glaciological constraints on current ice mass changes from modelling the ice sheets over the glacial cycles

    NASA Astrophysics Data System (ADS)

    Huybrechts, P.

    2003-04-01

    The evolution of continental ice sheets introduces a long time scale in the climate system. Large ice sheets have a memory of millenia, hence the present-day ice sheets of Greenland and Antarctica are still adjusting to climatic variations extending back to the last glacial period. This trend is separate from the direct response to mass-balance changes on decadal time scales and needs to be correctly accounted for when assessing current and future contributions to sea level. One way to obtain estimates of current ice mass changes is to model the past history of the ice sheets and their underlying beds over the glacial cycles. Such calculations assist to distinguish between the longer-term ice-dynamic evolution and short-term mass-balance changes when interpreting altimetry data, and are helpful to isolate the effects of postglacial rebound from gravity and altimetry trends. The presentation will discuss results obtained from 3-D thermomechanical ice-sheet/lithosphere/bedrock models applied to the Antarctic and Greenland ice sheets. The simulations are forced by time-dependent boundary conditions derived from sediment and ice core records and are constrained by geomorphological and glacial-geological data of past ice sheet and sea-level stands. Current simulations suggest that the Greenland ice sheet is close to balance, while the Antarctic ice sheet is still losing mass, mainly due to incomplete grounding-line retreat of the West Antarctic ice sheet since the LGM. The results indicate that altimetry trends are likely dominated by ice thickness changes but that the gravitational signal mainly reflects postglacial rebound.

  12. Can we define an asymptotic value for the ice active surface site density for heterogeneous ice nucleation?

    NASA Astrophysics Data System (ADS)

    Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank

    2015-04-01

    The formation of ice in atmospheric clouds has a substantial influence on the radiative properties of clouds as well as on the formation of precipitation. Therefore much effort has been made to understand and quantify the major ice formation processes in clouds. Immersion freezing has been suggested to be a dominant primary ice formation process in low and mid-level clouds (mixed-phase cloud conditions). It also has been shown that mineral dust particles are the most abundant ice nucleating particles in the atmosphere and thus may play an important role for atmospheric ice nucleation (Murray et al., 2012). Additionally, biological particles like bacteria and pollen are suggested to be potentially involved in atmospheric ice formation, at least on a regional scale (Murray et al., 2012). In recent studies for biological particles (SNOMAX and birch pollen), it has been demonstrated that freezing is induced by ice nucleating macromolecules and that an asymptotic value for the mass density of these ice nucleating macromolecules can be determined (Hartmann et al., 2013; Augustin et al., 2013, Wex et al., 2014). The question arises whether such an asymptotic value can also be determined for the ice active surface site density ns, a parameter which is commonly used to describe the ice nucleation activity of e.g., mineral dust. Such an asymptotic value for ns could be an important input parameter for atmospheric modeling applications. In the presented study, we therefore investigated the immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). For all particle sizes considered in the experiments, we observed a leveling off of the frozen droplet fraction reaching a plateau within the heterogeneous freezing temperature regime (T > -38°C) which was proportional to the particle surface area. Based on these findings, we could determine an asymptotic value for the ice

  13. Ice-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial ice masses

    NASA Astrophysics Data System (ADS)

    Wohlleben, Trudy M. H.

    Canadian High Arctic terrestrial ice masses and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow/ice-albedo feedback (where area changes in snow and/or ice cause changes in surface albedo and surface air temperatures, leading to further area changes in snow/ice); and (2) The elevation - mass balance feedback (where thickness changes in terrestrial ice masses cause changes to atmospheric circulation and precipitation patterns, leading to further ice thickness changes). In this thesis, numerical experiments are performed to: (1) quantify the magnitudes of the two feedbacks for chosen Canadian High Arctic terrestrial ice masses; and (2) to examine the direct and indirect consequences of surface air temperature changes upon englacial temperatures with implications for ice flow, mass flux divergence, and topographic evolution. Model results show that: (a) for John Evans Glacier, Ellesmere Island, the magnitude of the terrestrial snow/ice-albedo feedback can locally exceed that of sea ice on less than decadal timescales, with implications for glacier response times to climate perturbations; (b) although historical air temperature changes might be the direct cause of measured englacial temperature anomalies in various glacier and ice cap accumulation zones, they can also be the indirect cause of their enhanced diffusive loss; (c) while the direct result of past air temperature changes has been to cool the interior of John Evans Glacier, and its bed, the indirect result has been to create and maintain warm (pressure melting point) basal temperatures in the ablation zone; and (d) for Devon Ice Cap, observed mass gains in the northwest sector of the ice cap would be smaller without orographic precipitation and the mass balance---elevation feedback, supporting the hypothesis that this feedback is playing a role in the

  14. Investigating ice shelf mass loss processes from continuous satellite altimetry

    NASA Astrophysics Data System (ADS)

    Fricker, H. A.

    2017-12-01

    The Antarctic Ice Sheet continually gains mass through snowfall over its large area and, to remain approximately in equilibrium, it sheds most of this excess mass through two processes, basal melting and iceberg calving, that both occur in the floating ice shelves surrounding the continent. Small amounts of mass are also lost by surface melting, which occurs on many ice shelves every summer to varying degrees, and has been linked to ice-shelf collapse via hydrofracture on ice shelves that have been pre-weakened. Ice shelves provide mechanical support to `buttress' seaward flow of grounded ice, so that ice-shelf thinning and retreat result in enhanced ice discharge to the ocean. Ice shelves are susceptible to changes in forcing from both the atmosphere and the ocean, which both change on a broad range of timescales to modify mass gains and losses at the surface and base, and from internal instabilities of the ice sheet itself. Mass loss from iceberg calving is episodic, with typical intervals between calving events on the order of decades. Since ice shelves are so vast, the only viable way to monitor them is with satellites. Here, we discuss results from satellite radar and laser altimeter data from one NASA satellite (ICESat), and four ESA satellites (ERS-1, ERS-2, Envisat, CryoSat-2) to obtain estimates of ice-shelf surface height since the early 1990s. The continuous time series show accelerated losses in total Antarctic ice-shelf volume from 1994 to 2017, and allow us to investigate the processes causing ice-shelf mass change. For Larsen C, much of the variability comes from changing atmospheric conditions affecting firn state. In the Amundsen Sea, the rapid thinning is a combination of accelerated ocean-driven thinning and ice dynamics. This long-term thinning signal is, however, is strongly modulated by ENSO-driven interannual variability. However, observations of ocean variability around Antarctica are sparse, since these regions are often covered in sea ice

  15. Dual-sensor mapping of mass balance on Russia's northernmost ice caps

    NASA Astrophysics Data System (ADS)

    Nikolskiy, D.; Malinnikov, V.; Sharov, A.; Ukolova, M.

    2012-04-01

    th century. Hence only net balance values were determined for those ice caps. Other ice caps belong to the category of slow-moving or passive glaciers with simpler estimation of mass balance characteristics. Glacier elevation changes on several study glaciers were repeatedly determined with ICESat GLA06 data releases 28 and 29, and statistically compared. The root mean square difference between test determinations was given as less than 1 m rms and the lidar oversaturation effect was neglected in further work. Modern outlines of maritime glacier faces were corrected with the high-resolution optical quicklook imagery obtained from WorldView and QuickBird satellites. The research revealed the reduction of glacier area and general lowering of the glacier surface on most ice caps. Several new islets were discovered due to the glacial retreat in northern parts of Eva-Liv, Schmidt and Komsomolets islands. The cumulative mass budget in the study region remained negative while individual rates of volume change varied from -0.09 km3/a to +0.04 km3/a. Positive values of average mass balance with the maximum accumulation signal of approx. 0.9 m/a were determined on Ushakova, Schmidt and Henrietta ice caps. The results were represented in the form of glacier change maps with 50-m grid at 1:200,000 scale. The vertical accuracy of glacier change maps proved on several small and large ice caps was given as ± 0.3 m/a rms. Several resultant maps can be accessed at http://dib.joanneum.at/MAIRES/index.php?page=products. Further sub-regional comparison of glacier change maps with climatological, oceanographic, rheological, gravimetric and other ground-truth and EO data showed that spatial changes of insular glaciers are closely dependent on the frequency of precipitation events, water depth, sea ice regime, polynyas and gravity anomalies nearby. New opportunities for validating mass changes on the largest study glaciers and determining their bulk density are expected from the next

  16. Recent Changes in Ices Mass Balance of the Amundsen Sea Sector

    NASA Astrophysics Data System (ADS)

    Sutterley, T. C.; Velicogna, I.; Rignot, E. J.; Mouginot, J.; Flament, T.; van den Broeke, M. R.; van Wessem, M.; Reijmer, C.

    2014-12-01

    The glaciers flowing into the Amundsen Sea Embayment (ASE) sector of West Antarctica were confirmed in the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) to be the dominant contributors to the current Antarctic ice mass loss, and recently recognized to be undergoing marine ice sheet instability. Here, we investigate their regional ice mass balance using a time series of satellite and airborne data combined with model output products from the Regional Atmospheric and Climate Model (RACMO). Our dataset includes laser altimetry from NASA's ICESat-1 satellite mission and from Operation IceBridge (OIB) airborne surveys, satellite radar altimetry data from ESA's Envisat mission, time-variable gravity data from NASA/DLR's GRACE mission, surface mass balance products from RACMO, ice velocity from a combination of international synthetic aperture radar satellites and ice thickness data from OIB. We find a record of ice mass balance for the ASE where all the analyzed techniques agree remarkably in magnitude and temporal variability. The mass loss of the region has been increasing continuously since 1992, with no indication of a slow down. The mass loss during the common period averaged 91 Gt/yr and accelerated 20 Gt/yr2. In 1992-2013, the ASE contributed 4.5 mm global sea level rise. Overall, our results demonstrate the synergy of multiple analysis techniques for examining Antarctic Ice Sheet mass balance at the regional scale. This work was performed at UCI and JPL under a contract with NASA.

  17. Clouds enhance Greenland ice sheet mass loss

    NASA Astrophysics Data System (ADS)

    Van Tricht, Kristof; Gorodetskaya, Irina V.; L'Ecuyer, Tristan; Lenaerts, Jan T. M.; Lhermitte, Stef; Noel, Brice; Turner, David D.; van den Broeke, Michiel R.; van Lipzig, Nicole P. M.

    2015-04-01

    Clouds have a profound influence on both the Arctic and global climate, while they still represent one of the key uncertainties in climate models, limiting the fidelity of future climate projections. The potentially important role of thin liquid-containing clouds over Greenland in enhancing ice sheet melt has recently gained interest, yet current research is spatially and temporally limited, focusing on particular events, and their large scale impact on the surface mass balance remains unknown. We used a combination of satellite remote sensing (CloudSat - CALIPSO), ground-based observations and climate model (RACMO) data to show that liquid-containing clouds warm the Greenland ice sheet 94% of the time. High surface reflectivity (albedo) for shortwave radiation reduces the cloud shortwave cooling effect on the absorbed fluxes, while not influencing the absorption of longwave radiation. Cloud warming over the ice sheet therefore dominates year-round. Only when albedo values drop below ~0.6 in the coastal areas during summer, the cooling effect starts to overcome the warming effect. The year-round excess of energy due to the presence of liquid-containing clouds has an extensive influence on the mass balance of the ice sheet. Simulations using the SNOWPACK snow model showed not only a strong influence of these liquid-containing clouds on melt increase, but also on the increased sublimation mass loss. Simulations with the Community Earth System Climate Model for the end of the 21st century (2080-2099) show that Greenland clouds contain more liquid water path and less ice water path. This implies that cloud radiative forcing will be further enhanced in the future. Our results therefore urge the need for improving cloud microphysics in climate models, to improve future projections of ice sheet mass balance and global sea level rise.

  18. Trends in ice sheet mass balance, 1992 to 2017

    NASA Astrophysics Data System (ADS)

    Shepherd, A.; Ivins, E. R.; Smith, B.; Velicogna, I.; Whitehouse, P. L.; Rignot, E. J.; van den Broeke, M. R.; Briggs, K.; Hogg, A.; Krinner, G.; Joughin, I. R.; Nowicki, S.; Payne, A. J.; Scambos, T.; Schlegel, N.; Moyano, G.; Konrad, H.

    2017-12-01

    The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a community effort, jointly supported by ESA and NASA, that aims to provide a consensus estimate of ice sheet mass balance from satellite gravimetry, altimetry and mass budget assessments, on an annual basis. The project has five experiment groups, one for each of the satellite techniques and two others to analyse surface mass balance (SMB) and glacial isostatic adjustment (GIA). The basic premise for the exercise is that individual ice sheet mass balance datasets are generated by project participants using common spatial and temporal domains to allow meaningful inter-comparison, and this controlled comparison in turn supports aggregation of the individual datasets over their full period. Participation is open to the full community, and the quality and consistency of submissions is regulated through a series of data standards and documentation requirements. The second phase of IMBIE commenced in 2015, with participant data submitted in 2016 and a combined estimate due for public release in 2017. Data from 48 participant groups were submitted to one of the three satellite mass balance technique groups or to the ancillary dataset groups. The individual mass balance estimates and ancillary datasets have been compared and combined within the respective groups. Following this, estimates of ice sheet mass balance derived from the individual techniques were then compared and combined. The result is single estimates of ice sheet mass balance for Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula. The participants, methodology and results of the exercise will be presented in this paper.

  19. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013

    NASA Astrophysics Data System (ADS)

    Seo, Ki-Weon; Wilson, Clark R.; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E.; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-05-01

    Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr2. Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr2. Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr2.

  20. Surface Mass Balance Contributions to Acceleration of Antarctic Ice Mass Loss during 2003- 2013

    NASA Astrophysics Data System (ADS)

    Seo, K. W.; Wilson, C. R.; Scambos, T. A.; Kim, B. M.; Waliser, D. E.; Tian, B.; Kim, B.; Eom, J.

    2015-12-01

    Recent observations from satellite gravimetry (the GRACE mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6±7.2 GTon/yr2. Of this total, we find that the surface mass balance component is -8.2±2.0 GTon/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8±5.8 GTon/yr2. Correcting for this yields an ice discharge acceleration of -15.1±6.5 GTon/yr2.

  1. Developing a bubble number-density paleoclimatic indicator for glacier ice

    USGS Publications Warehouse

    Spencer, M.K.; Alley, R.B.; Fitzpatrick, J.J.

    2006-01-01

    Past accumulation rate can be estimated from the measured number-density of bubbles in an ice core and the reconstructed paleotemperature, using a new technique. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. An empirical model of these processes, optimized to fit published data on recently formed bubbles, reconstructs accumulation rates using recent temperatures with an uncertainty of 41% (P < 0.05). For modern sites considered here, no statistically significant trend exists between mean annual temperature and the ratio of bubble number-density to grain number-density at the time of pore close-off; optimum modeled accumulation-rate estimates require an eventual ???2.02 ?? 0.08 (P < 0.05) bubbles per close-off grain. Bubble number-density in the GRIP (Greenland) ice core is qualitatively consistent with independent estimates for a combined temperature decrease and accumulation-rate increase there during the last 5 kyr.

  2. The glass transition in high-density amorphous ice

    PubMed Central

    Loerting, Thomas; Fuentes-Landete, Violeta; Handle, Philip H.; Seidl, Markus; Amann-Winkel, Katrin; Gainaru, Catalin; Böhmer, Roland

    2015-01-01

    There has been a long controversy regarding the glass transition in low-density amorphous ice (LDA). The central question is whether or not it transforms to an ultraviscous liquid state above 136 K at ambient pressure prior to crystallization. Currently, the most widespread interpretation of the experimental findings is in terms of a transformation to a superstrong liquid above 136 K. In the last decade some work has also been devoted to the study of the glass transition in high-density amorphous ice (HDA) which is in the focus of the present review. At ambient pressure HDA is metastable against both ice I and LDA, whereas at > 0.2 GPa HDA is no longer metastable against LDA, but merely against high-pressure forms of crystalline ice. The first experimental observation interpreted as the glass transition of HDA was made using in situ methods by Mishima, who reported a glass transition temperature Tg of 160 K at 0.40 GPa. Soon thereafter Andersson and Inaba reported a much lower glass transition temperature of 122 K at 1.0 GPa. Based on the pressure dependence of HDA's Tg measured in Innsbruck, we suggest that they were in fact probing the distinct glass transition of very high-density amorphous ice (VHDA). Very recently the glass transition in HDA was also observed at ambient pressure at 116 K. That is, LDA and HDA show two distinct glass transitions, clearly separated by about 20 K at ambient pressure. In summary, this suggests that three glass transition lines can be defined in the p–T plane for LDA, HDA, and VHDA. PMID:25641986

  3. The glass transition in high-density amorphous ice.

    PubMed

    Loerting, Thomas; Fuentes-Landete, Violeta; Handle, Philip H; Seidl, Markus; Amann-Winkel, Katrin; Gainaru, Catalin; Böhmer, Roland

    2015-01-01

    There has been a long controversy regarding the glass transition in low-density amorphous ice (LDA). The central question is whether or not it transforms to an ultraviscous liquid state above 136 K at ambient pressure prior to crystallization. Currently, the most widespread interpretation of the experimental findings is in terms of a transformation to a superstrong liquid above 136 K. In the last decade some work has also been devoted to the study of the glass transition in high-density amorphous ice (HDA) which is in the focus of the present review. At ambient pressure HDA is metastable against both ice I and LDA, whereas at > 0.2 GPa HDA is no longer metastable against LDA, but merely against high-pressure forms of crystalline ice. The first experimental observation interpreted as the glass transition of HDA was made using in situ methods by Mishima, who reported a glass transition temperature T g of 160 K at 0.40 GPa. Soon thereafter Andersson and Inaba reported a much lower glass transition temperature of 122 K at 1.0 GPa. Based on the pressure dependence of HDA's T g measured in Innsbruck, we suggest that they were in fact probing the distinct glass transition of very high-density amorphous ice (VHDA). Very recently the glass transition in HDA was also observed at ambient pressure at 116 K. That is, LDA and HDA show two distinct glass transitions, clearly separated by about 20 K at ambient pressure. In summary, this suggests that three glass transition lines can be defined in the p-T plane for LDA, HDA, and VHDA.

  4. A reconciled estimate of ice-sheet mass balance.

    PubMed

    Shepherd, Andrew; Ivins, Erik R; A, Geruo; Barletta, Valentina R; Bentley, Mike J; Bettadpur, Srinivas; Briggs, Kate H; Bromwich, David H; Forsberg, René; Galin, Natalia; Horwath, Martin; Jacobs, Stan; Joughin, Ian; King, Matt A; Lenaerts, Jan T M; Li, Jilu; Ligtenberg, Stefan R M; Luckman, Adrian; Luthcke, Scott B; McMillan, Malcolm; Meister, Rakia; Milne, Glenn; Mouginot, Jeremie; Muir, Alan; Nicolas, Julien P; Paden, John; Payne, Antony J; Pritchard, Hamish; Rignot, Eric; Rott, Helmut; Sørensen, Louise Sandberg; Scambos, Ted A; Scheuchl, Bernd; Schrama, Ernst J O; Smith, Ben; Sundal, Aud V; van Angelen, Jan H; van de Berg, Willem J; van den Broeke, Michiel R; Vaughan, David G; Velicogna, Isabella; Wahr, John; Whitehouse, Pippa L; Wingham, Duncan J; Yi, Donghui; Young, Duncan; Zwally, H Jay

    2012-11-30

    We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods--especially in Greenland and West Antarctica--and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 ± 49, +14 ± 43, -65 ± 26, and -20 ± 14 gigatonnes year(-1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year(-1) to the rate of global sea-level rise.

  5. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013.

    PubMed

    Seo, Ki-Weon; Wilson, Clark R; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-05-01

    Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr 2 . Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr 2 . However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr 2 . Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr 2 .

  6. A Reconciled Estimate of Ice-Sheet Mass Balance

    NASA Technical Reports Server (NTRS)

    Shepherd, Andrew; Ivins, Erik R.; Geruo, A.; Barletta, Valentia R.; Bentley, Mike J.; Bettadpur, Srinivas; Briggs, Kate H.; Bromwich, David H.; Forsberg, Rene; Galin, Natalia; hide

    2012-01-01

    We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods-especially in Greenland and West Antarctica-and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 plus or minus 49, +14 plus or minus 43, -65 plus or minus 26, and -20 plus or minus 14 gigatonnes year(sup -1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 plus or minus 0.20 millimeter year(sup -1) to the rate of global sea-level rise.

  7. Ice-coupled wave propagation across an abrupt change in ice rigidity, density, or thickness

    NASA Astrophysics Data System (ADS)

    Barrett, Murray D.; Squire, Vernon A.

    1996-09-01

    The model of Fox and Squire [1990, 1991, 1994], which discusses the oblique propagation of surface gravity waves from the open sea into an ice sheet of constant thickness and properties, is augmented to include propagation across an abrupt transition of properties within a continuous ice sheet or across two dissimilar ice sheets that abut one another but are free to move independently. Rigidity, thickness, and/or density may change across the transition, allowing, for example, the modeling of ice-coupled waves into, across, and out of refrozen leads and polynyas, across cracks, and through coherent pressure ridges. Reflection and transmission behavior is reported for various changes in properties under both types of transition conditions.

  8. The Greenland Ice Sheet's surface mass balance in a seasonally sea ice-free Arctic

    NASA Astrophysics Data System (ADS)

    Day, J. J.; Bamber, J. L.; Valdes, P. J.

    2013-09-01

    General circulation models predict a rapid decrease in sea ice extent with concurrent increases in near-surface air temperature and precipitation in the Arctic over the 21st century. This has led to suggestions that some Arctic land ice masses may experience an increase in accumulation due to enhanced evaporation from a seasonally sea ice-free Arctic Ocean. To investigate the impact of this phenomenon on Greenland Ice Sheet climate and surface mass balance (SMB), a regional climate model, HadRM3, was used to force an insolation-temperature melt SMB model. A set of experiments designed to investigate the role of sea ice independently from sea surface temperature (SST) forcing are described. In the warmer and wetter SI + SST simulation, Greenland experiences a 23% increase in winter SMB but 65% reduced summer SMB, resulting in a net decrease in the annual value. This study shows that sea ice decline contributes to the increased winter balance, causing 25% of the increase in winter accumulation; this is largest in eastern Greenland as the result of increased evaporation in the Greenland Sea. These results indicate that the seasonal cycle of Greenland's SMB will increase dramatically as global temperatures increase, with the largest changes in temperature and precipitation occurring in winter. This demonstrates that the accurate prediction of changes in sea ice cover is important for predicting Greenland SMB and ice sheet evolution.

  9. Convergence on the Prediction of Ice Particle Mass and Projected Area in Ice Clouds

    NASA Astrophysics Data System (ADS)

    Mitchell, D. L.

    2013-12-01

    Ice particle mass- and area-dimensional power law (henceforth m-D and A-D) relationships are building-blocks for formulating microphysical processes and optical properties in cloud and climate models, and they are critical for ice cloud remote sensing algorithms, affecting the retrieval accuracy. They can be estimated by (1) directly measuring the sizes, masses and areas of individual ice particles at ground-level and (2) using aircraft probes to simultaneously measure the ice water content (IWC) and ice particle size distribution. A third indirect method is to use observations from method 1 to develop an m-A relationship representing mean conditions in ice clouds. Owing to a tighter correlation (relative to m-D data), this m-A relationship can be used to estimate m from aircraft probe measurements of A. This has the advantage of estimating m at small sizes, down to 10 μm using the 2D-Sterio probe. In this way, 2D-S measurements of maximum dimension D can be related to corresponding estimates of m to develop ice cloud type and temperature dependent m-D expressions. However, these expressions are no longer linear in log-log space, but are slowly varying curves covering most of the size range of natural ice particles. This work compares all three of the above methods and demonstrates close agreement between them. Regarding (1), 4869 ice particles and corresponding melted hemispheres were measured during a field campaign to obtain D and m. Selecting only those unrimed habits that formed between -20°C and -40°C, the mean mass values for selected size intervals are within 35% of the corresponding masses predicted by the Method 3 curve based on a similar temperature range. Moreover, the most recent m-D expression based on Method 2 differs by no more than 50% with the m-D curve from Method 3. Method 3 appears to be the most accurate over the observed ice particle size range (10-4000 μm). An m-D/A-D scheme was developed by which self-consistent m-D and A-D power laws

  10. Use of a Tea Infuser to Submerge Low-Density Dry Ice

    ERIC Educational Resources Information Center

    Fictorie, Carl P.; Vitz, Ed

    2004-01-01

    A simple tea infuser is obtained and been used as a container for the dry ice to simulate the effect from high-density dry ice. The tea infuser is a simple, low cost device to allow instructors with access to dry ice makers to effectively use the interesting demonstration.

  11. Understanding Recent Mass Balance Changes of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelius

    2003-01-01

    The ultimate goal of this project is to better understand the current transfer of mass between the Greenland Ice Sheet, the world's oceans and the atmosphere, and to identify processes controlling the rate of this transfer, to be able to predict with greater confidence future contributions to global sea level rise. During the first year of this project, we focused on establishing longer-term records of change of selected outlet glaciers, reevaluation of mass input to the ice sheet and analysis of climate records derived from ice cores, and modeling meltwater production and runoff from the margins of the ice sheet.

  12. Antarctic Glacial Isostatic Adjustment and Ice Sheet Mass Balance using GRACE: A Report from the Ice-sheet Mass Balance Exercise (IMBIE)

    NASA Astrophysics Data System (ADS)

    Ivins, E. R.; Wahr, J. M.; Schrama, E. J.; Milne, G. A.; Barletta, V.; Horwath, M.; Whitehouse, P.

    2012-12-01

    In preparation for the Inter-govermental Panel on Climate Change: Assessment Report 5 (IPCC AR5), ESA and NASA have formed a committee of experts to perform a formal set of comparative experiments concerning space observations of ice sheet mass balance. This project began in August of 2011 and has now concluded with a report submitted for Science (Shepherd et al., 2012). The focus of the work conducted is to re-evaluate scientific reports on the mass balance of Greenland ice sheet (GIS) and Antarctic ice sheet (AIS). The most serious discrepancies have been reported for the AIS, amounting to as much as 0.9 mm/yr in discrepant sea level contribution. A direct method of determining the AIS is by space gravimetry. However, for this method to contribute to our understanding of sea level change, we require knowledge of present-day non-elastic vertical movements of bedrock in Antarctica. Quantifying the uncertainty and bias caused by lack of observational control on models of regional glacial isostatic adjustment (GIA), was a major focus for our experiments. This regional process is the most problematic error source for GRACE-determinations of ice mass balance in Antarctica. While GIA likely dominates some large vertical motions in Antarctica that are now observed with GPS (Thomas et al., 2011, GRL), interpretations still require models. The reported uncertainty for space gravimetric (GRACE) based sea level sourcing is roughly 0.20 to 0.35 mm/yr. The uncertainty is also part of the error budget for mass balances derived from altimetry measurements, though at a much lower level. Analysis of the GRACE time series using CSR RL04 (2003.0-2010.10) for AIS mass balance reveals a small trend of order +1 to -24 Gt/yr without a GIA correction. Three periods were selected over which to perform inter-comparisons (see Table). One class of GIA models, that relies primarily on far field sea level reconstructions (e.g. ICE-5G), provide a GIA correction that places AIS mass imbalance (

  13. Devon Ice cap's future: results from climate and ice dynamics modelling via surface mass balance modelling

    NASA Astrophysics Data System (ADS)

    Rodehacke, C. B.; Mottram, R.; Boberg, F.

    2017-12-01

    The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we various boundary conditions, ranging from ERA-Interim reanalysis data via global climate model high resolution (5km) output from the regional climate model HIRHAM5, to determine the surface mass balance of the Devon ice cap. These SMB estimates are used to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.

  14. The Mass Surface Density Distribution of a High-Mass Protocluster forming from an IRDC and GMC

    NASA Astrophysics Data System (ADS)

    Lim, Wanggi; Tan, Jonathan C.; Kainulainen, Jouni; Ma, Bo; Butler, Michael

    2016-01-01

    We study the probability distribution function (PDF) of mass surface densities of infrared dark cloud (IRDC) G028.36+00.07 and its surrounding giant molecular cloud (GMC). Such PDF analysis has the potential to probe the physical processes that are controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 parsecs, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a high-mass, "super star cluster". We study mass surface densities in two ways. First, we use a combination of NIR, MIR and FIR extinction maps that are able to probe the bulk of the cloud structure that is not yet forming stars. This analysis also shows evidence for flattening of the IR extinction law as mass surface density increases, consistent with increasing grain size and/or growth of ice mantles. Second, we study the FIR and sub-mm dust continuum emission from the cloud, especially utlizing Herschel PACS and SPIRE images. We first subtract off the contribution of the foreground diffuse emission that contaminates these images. Next we examine the effects of background subtraction and choice of dust opacities on the derived mass surface density PDF. The final derived PDFs from both methods are compared, including also with other published studies of this cloud. The implications for theoretical models and simulations of cloud structure, including the role of turbulence and magnetic fields, are discussed.

  15. Antarctic Ice-Sheet Mass Balance from Satellite Altimetry 1992 to 2001

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Brenner, Anita C.; Cornejo, Helen; Giovinetto, Mario; Saba, Jack L.; Yi, Donghui

    2003-01-01

    A major uncertainty in understanding the causes of the current rate of sea level rise is the potential contributions from mass imbalances of the Greenland and Antarctic ice sheets. Estimates of the current mass balance of the Antarctic ice sheet are derived from surface- elevation changes obtained from 9 years of ERS - 1 & 2 radar altimeter data. Elevation time-series are created from altimeter crossovers among 90-day data periods on a 50 km grid to 81.5 S. The time series are fit with a multivariate linear/sinusoidal function to give the average rate of elevation change (dH/dt). On the major Rome-Filchner, Ross, and Amery ice shelves, the W d t are small or near zero. In contrast, the ice shelves of the Antarctic Peninsula and along the West Antarctic coast appear to be thinning significantly, with a 23 +/- 3 cm per year surface elevation decrease on the Larsen ice shelf and a 65 +/- 4 cm per year decrease on the Dotson ice shelf. On the grounded ice, significant elevation decreases are obtained over most of the drainage basins of the Pine Island and Thwaites glaciers in West Antarctica and inland of Law Dome in East Antarctica. Significant elevation increases are observed within about 200 km of the coast around much of the rest of the ice sheet. Farther inland, the changes are a mixed pattern of increases and decreases with increases of a few centimeters per year at the highest elevations of the East Antarctic plateau. The derived elevation changes are combined with estimates of the bedrock uplift from several models to provide maps of ice thickness change. The ice thickness changes enable estimates of the ice mass balances for the major drainage basins, the overall mass balance, and the current contribution of the ice sheet to global sea level change.

  16. Greenland Ice Sheet Mass Balance: Distribution of Increased Mass Loss with Climate Warming; 2003-07 Versus 1992-2002

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Benner, Anita C.; Beckley, Matthew; Cornejo, Helen G.; DiMarzio, John; Giovinetto, Mario B.; Neumann, Thomas A.; Robbins, John; Saba, Jack L.; hide

    2011-01-01

    We derive mass changes of the Greenland ice sheet (GIS) for 2003-07 from ICESat laser altimetry and compare them with results for 1992-2002 from ERS radar and airborne laser altimetry. The GIS continued to grow inland and thin at the margins during 2003 07, but surface melting and accelerated flow significantly increased the marginal thinning compared with the 1990s. The net balance changed from a small loss of 7 plus or minus 3 Gt a 1(sup -1) in the 1990s to 171 plus or minus 4 Gt a (sup -1) for 2003-07, contributing 0.5 mm a(sup -1) to recent global sea-level rise. We divide the derived mass changes into two components: (1) from changes in melting and ice dynamics and (2) from changes in precipitation and accumulation rate. We use our firn compaction model to calculate the elevation changes driven by changes in both temperature and accumulation rate and to calculate the appropriate density to convert the accumulation-driven changes to mass changes. Increased losses from melting and ice dynamics (17-206 Gt a(sup-1) are over seven times larger than increased gains from precipitation (10 35 Gt a(sup-1) during a warming period of approximately 2 K (10 a)(sup -1) over the GIS. Above 2000m elevation, the rate of gain decreased from 44 to 28 Gt a(sup-1), while below 2000m the rate of loss increased from 51 to 198 Gt a(sup-1). Enhanced thinning below the equilibrium line on outlet glaciers indicates that increased melting has a significant impact on outlet glaciers, as well as accelerating ice flow. Increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales.

  17. Overview of Ice-Sheet Mass Balance and Dynamics from ICESat Measurements

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay

    2010-01-01

    The primary purpose of the ICESat mission was to determine the present-day mass balance of the Greenland and Antarctic ice sheets, identify changes that may be occurring in the surface-mass flux and ice dynamics, and estimate their contributions to global sea-level rise. Although ICESat's three lasers were planned to make continuous measurements for 3 to 5 years, the mission was re-planned to operate in 33-day campaigns 2 to 3 times each year following failure of the first laser after 36 days. Seventeen campaigns were conducted with the last one in the Fall of 2009. Mass balance maps derived from measured ice-sheet elevation changes show that the mass loss from Greenland has increased significantly to about 170 Gt/yr for 2003 to 2007 from a state of near balance in the 1990's. Increased losses (189 Gt/yr) from melting and dynamic thinning are over seven times larger'than increased gains (25 gt/yr) from precipitation. Parts of the West Antarctic ice sheet and the Antarctic Peninsula are losing mass at an increasing rate, but other parts of West Antarctica and the East Antarctic ice sheet are gaining mass at an increasing rate. Increased losses of 35 Gt/yr in Pine Island, Thwaites-Smith, and Marie-Bryd.Coast are more than balanced by gains in base of Peninsula and ice stream C, D, & E systems. From the 1992-2002 to 2003-2007 period, the overall mass balance for Antarctica changed from a loss of about 60 Gt/yr to near balance or slightly positive.

  18. Excess electrons in ice: a density functional theory study.

    PubMed

    Bhattacharya, Somesh Kr; Inam, Fakharul; Scandolo, Sandro

    2014-02-21

    We present a density functional theory study of the localization of excess electrons in the bulk and on the surface of crystalline and amorphous water ice. We analyze the initial stages of electron solvation in crystalline and amorphous ice. In the case of crystalline ice we find that excess electrons favor surface states over bulk states, even when the latter are localized at defect sites. In contrast, in amorphous ice excess electrons find it equally favorable to localize in bulk and in surface states which we attribute to the preexisting precursor states in the disordered structure. In all cases excess electrons are found to occupy the vacuum regions of the molecular network. The electron localization in the bulk of amorphous ice is assisted by its distorted hydrogen bonding network as opposed to the crystalline phase. Although qualitative, our results provide a simple interpretation of the large differences observed in the dynamics and localization of excess electrons in crystalline and amorphous ice films on metals.

  19. Radar Interferometry Studies of the Mass Balance of Polar Ice Sheets

    NASA Technical Reports Server (NTRS)

    Rignot, Eric (Editor)

    1999-01-01

    The objectives of this work are to determine the current state of mass balance of the Greenland and Antarctic Ice Sheets. Our approach combines different techniques, which include satellite synthetic-aperture radar interferometry (InSAR), radar and laser altimetry, radar ice sounding, and finite-element modeling. In Greenland, we found that 3.5 times more ice flows out of the northern part of the Greenland Ice Sheet than previously accounted for. The discrepancy between current and past estimates is explained by extensive basal melting of the glacier floating sections in the proximity of the grounding line where the glacier detaches from its bed and becomes afloat in the ocean. The inferred basal melt rates are very large, which means that the glaciers are very sensitive to changes in ocean conditions. Currently, it appears that the northern Greenland glaciers discharge more ice than is being accumulated in the deep interior, and hence are thinning. Studies of temporal changes in grounding line position using InSAR confirm the state of retreat of northern glaciers and suggest that thinning is concentrated at the lower elevations. Ongoing work along the coast of East Greenland reveals an even larger mass deficit for eastern Greenland glaciers, with thinning affecting the deep interior of the ice sheet. In Antarctica, we found that glaciers flowing into a large ice shelf system, such as the Ronne Ice Shelf in the Weddell Sea, exhibit an ice discharge in remarkable agreement with mass accumulation in the interior, and the glacier grounding line positions do not migrate with time. Glaciers flowing rapidly into the Amudsen Sea, unrestrained by a major ice shelf, are in contrast discharging more ice than required to maintain a state of mass balance and are thinning quite rapidly near the coast. The grounding line of Pine Island glacier (see diagram) retreated 5 km in 4 years, which corresponds to a glacier thinning rate of 3.5 m/yr. Mass imbalance is even more negative

  20. High-density amorphous ice: A path-integral simulation

    NASA Astrophysics Data System (ADS)

    Herrero, Carlos P.; Ramírez, Rafael

    2012-09-01

    Structural and thermodynamic properties of high-density amorphous (HDA) ice have been studied by path-integral molecular dynamics simulations in the isothermal-isobaric ensemble. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. Quantum nuclear motion is found to affect several observable properties of the amorphous solid. At low temperature (T = 50 K) the molar volume of HDA ice is found to increase by 6%, and the intramolecular O-H distance rises by 1.4% due to quantum motion. Peaks in the radial distribution function of HDA ice are broadened with respect to their classical expectancy. The bulk modulus, B, is found to rise linearly with the pressure, with a slope ∂B/∂P = 7.1. Our results are compared with those derived earlier from classical and path-integral simulations of HDA ice. We discuss similarities and discrepancies with those earlier simulations.

  1. Sea Ice Mass Reconciliation Exercise (SIMRE) for altimetry derived sea ice thickness data sets

    NASA Astrophysics Data System (ADS)

    Hendricks, S.; Haas, C.; Tsamados, M.; Kwok, R.; Kurtz, N. T.; Rinne, E. J.; Uotila, P.; Stroeve, J.

    2017-12-01

    Satellite altimetry is the primary remote sensing data source for retrieval of Arctic sea-ice thickness. Observational data sets are available from current and previous missions, namely ESA's Envisat and CryoSat as well as NASA ICESat. In addition, freeboard results have been published from the earlier ESA ERS missions and candidates for new data products are the Sentinel-3 constellation, the CNES AltiKa mission and NASA laser altimeter successor ICESat-2. With all the different aspects of sensor type and orbit configuration, all missions have unique properties. In addition, thickness retrieval algorithms have evolved over time and data centers have developed different strategies. These strategies may vary in choice of auxiliary data sets, algorithm parts and product resolution and masking. The Sea Ice Mass Reconciliation Exercise (SIMRE) is a project by the sea-ice radar altimetry community to bridge the challenges of comparing data sets across missions and algorithms. The ESA Arctic+ research program facilitates this project with the objective to collect existing data sets and to derive a reconciled estimate of Arctic sea ice mass balance. Starting with CryoSat-2 products, we compare results from different data centers (UCL, AWI, NASA JPL & NASA GSFC) at full resolution along selected orbits with independent ice thickness estimates. Three regions representative of first-year ice, multiyear ice and mixed ice conditions are used to compare the difference in thickness and thickness change between products over the seasonal cycle. We present first results and provide an outline for the further development of SIMRE activities. The methodology for comparing data sets is designed to be extendible and the project is open to contributions by interested groups. Model results of sea ice thickness will be added in a later phase of the project to extend the scope of SIMRE beyond EO products.

  2. Ferroelectricity in high-density H 2O ice

    DOE PAGES

    Caracas, Razvan; Hemley, Russell J.

    2015-04-01

    The origin of longstanding anomalies in experimental studies of the dense solid phases of H 2O ices VII, VIII, and X is examined using a combination of first-principles theoretical methods. We find that a ferroelectric variant of ice VIII is energetically competitive with the established antiferroelectric form under pressure. The existence of domains of the ferroelectric form within anti-ferroelectric ice can explain previously observed splittings in x-ray diffraction data. The ferroelectric form is stabilized by density and is accompanied by the onset of spontaneous polarization. Here, the presence of local electric fields triggers the preferential parallel orientation of the watermore » molecules in the structure, which could be stabilized in bulk using new high-pressure techniques.« less

  3. Greenland ice sheet surface temperature, melt and mass loss: 2000-06

    USGS Publications Warehouse

    Hall, D.K.; Williams, R.S.; Luthcke, S.B.; DiGirolamo, N.E.

    2008-01-01

    A daily time series of 'clear-sky' surface temperature has been compiled of the Greenland ice sheet (GIS) using 1 km resolution moderate-resolution imaging spectroradiometer (MODIS) land-surface temperature (LST) maps from 2000 to 2006. We also used mass-concentration data from the Gravity Recovery and Climate Experiment (GRACE) to study mass change in relationship to surface melt from 2003 to 2006. The mean LST of the GIS increased during the study period by ???0.27??Ca-1. The increase was especially notable in the northern half of the ice sheet during the winter months. Melt-season length and timing were also studied in each of the six major drainage basins. Rapid (<15 days) and sustained mass loss below 2000 m elevation was triggered in 2004 and 2005 as recorded by GRACE when surface melt begins. Initiation of large-scale surface melt was followed rapidly by mass loss. This indicates that surface meltwater is flowing rapidly to the base of the ice sheet, causing acceleration of outlet glaciers, thus highlighting the metastability of parts of the GIS and the vulnerability of the ice sheet to air-temperature increases. If air temperatures continue to rise over Greenland, increased surface melt will play a large role in ice-sheet mass loss.

  4. Contribution of Deformation to Sea Ice Mass Balance: A Case Study From an N-ICE2015 Storm

    NASA Astrophysics Data System (ADS)

    Itkin, Polona; Spreen, Gunnar; Hvidegaard, Sine Munk; Skourup, Henriette; Wilkinson, Jeremy; Gerland, Sebastian; Granskog, Mats A.

    2018-01-01

    The fastest and most efficient process of gaining sea ice volume is through the mechanical redistribution of mass as a consequence of deformation events. During the ice growth season divergent motion produces leads where new ice grows thermodynamically, while convergent motion fractures the ice and either piles the resultant ice blocks into ridges or rafts one floe under the other. Here we present an exceptionally detailed airborne data set from a 9 km2 area of first year and second year ice in the Transpolar Drift north of Svalbard that allowed us to estimate the redistribution of mass from an observed deformation event. To achieve this level of detail we analyzed changes in sea ice freeboard acquired from two airborne laser scanner surveys just before and right after a deformation event brought on by a passing low-pressure system. A linear regression model based on divergence during this storm can explain 64% of freeboard variability. Over the survey region we estimated that about 1.3% of level sea ice volume was pressed together into deformed ice and the new ice formed in leads in a week after the deformation event would increase the sea ice volume by 0.5%. As the region is impacted by about 15 storms each winter, a simple linear extrapolation would result in about 7% volume increase and 20% deformed ice fraction at the end of the season.

  5. Ice nucleation in the upper troposphere: Sensitivity to aerosol number density, temperature, and cooling rate

    NASA Technical Reports Server (NTRS)

    Jensen, E. J.; Toon, O. B.

    1994-01-01

    We have investigated the processes that control ice crystal nucleation in the upper troposphere using a numerical model. Nucleation of ice resulting from cooling was simulated for a range of aerosol number densities, initial temperatures, and cooling rates. In contrast to observations of stratus clouds, we find that the number of ice crystals that nucleate in cirrus is relatively insensitive to the number of aerosols present. The ice crystal size distribution at the end of the nucleation process is unaffected by the assumed initial aerosol number density. Essentially, nucleation continues until enough ice crystals are present such that their deposition growth rapidly depletes the vapor and shuts off any further nucleation. However, the number of ice crystals nucleated increases rapidly with decreasing initial temperature and increasing cooling rate. This temperature dependence alone could explain the large ice crystal number density observed in very cold tropical cirrus.

  6. Antarctic and Greenland ice sheet mass balance products from satellite gravimetry

    NASA Astrophysics Data System (ADS)

    Horwath, Martin; Groh, Andreas; Horvath, Alexander; Forsberg, René; Meister, Rakia; Barletta, Valentina R.; Shepherd, Andrew

    2017-04-01

    Because of their important role in the Earth's climate system, ESA's Climate Change Initiative (CCI) has identified both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS) as Essential Climate Variables (ECV). Since respondents of a user survey indicated that the ice sheet mass balance is one of the most important ECV data products needed to better understand climate change, the AIS_cci and the GIS_cci project provide Gravimetric Mass Balance (GMB) products based on satellite gravimetry data. The GMB products are derived from GRACE (Gravity Recovery and Climate Experiment) monthly solutions of release ITSG-Grace2016 produced at TU Graz. GMB basin products (i.e. time series of monthly mass changes for the entire ice sheets and selected drainage basins) and GMB gridded products (e.g. mass balance estimates with a formal resolution of about 50km, covering the entire ice sheets) are generated for the period from 2002 until present. The first GMB product was released in mid 2016. Here we present an extended and updated version of the ESA CCI GMB products, which are freely available through data portals hosted by the projects (https://data1.geo.tu-dresden.de/ais_gmb, http://products.esa-icesheets-cci.org/products/downloadlist/GMB). Since the initial product release, the applied processing strategies have been improved in order to further reduce GRACE errors and to enhance the separation of signals super-imposed to the ice mass changes. While a regional integration approach is used by the AIS_cci project, the GMB products of the GIS_cci project are derived using a point mass inversion. The differences between both approaches are investigated through the example of the GIS, where an alternative GMB product was generated using the regional integration approach implemented by the AIS_cci. Finally, we present the latest mass balance estimates for both ice sheets as well as their corresponding contributions to global sea level rise.

  7. Surface mass balance of Greenland mountain glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.

    2009-12-01

    Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.

  8. Long term ice sheet mass change rates and inter-annual variability from GRACE gravimetry.

    NASA Astrophysics Data System (ADS)

    Harig, C.

    2017-12-01

    The GRACE time series of gravimetry now stretches 15 years since its launch in 2002. Here we use Slepian functions to estimate the long term ice mass trends of Greenland, Antarctica, and several glaciated regions. The spatial representation shows multi-year to decadal regional shifts in accelerations, in agreement with increases in radar derived ice velocity. Interannual variations in ice mass are of particular interest since they can directly link changes in ice sheets to the drivers of change in the polar ocean and atmosphere. The spatial information retained in Slepian functions provides a tool to determine how this link varies in different regions within an ice sheet. We present GRACE observations of the 2013-2014 slowdown in mass loss of the Greenland ice sheet, which was concentrated in specific parts of the ice sheet and in certain months of the year. We also discuss estimating the relative importance of climate factors that control ice mass balance, as a function of location of the glacier/ice cap as well as the spatial variation within an ice sheet by comparing gravimetry with observations of surface air temperature, ocean temperature, etc. as well as model data from climate reanalysis products.

  9. Accelerated West Antarctic ice mass loss continues to outpace East Antarctic gains

    NASA Astrophysics Data System (ADS)

    Harig, Christopher; Simons, Frederik J.

    2015-04-01

    While multiple data sources have confirmed that Antarctica is losing ice at an accelerating rate, different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy, spatio-temporal resolution, and coverage. Some scope remains for methodological improvements using a single data type. In this study we report our progress in increasing the accuracy and spatial resolution of time-variable gravimetry from the Gravity Recovery and Climate Experiment (GRACE). We determine the geographic pattern of ice mass change in Antarctica between January 2003 and June 2014, accounting for glacio-isostatic adjustment (GIA) using the IJ05_R2 model. Expressing the unknown signal in a sparse Slepian basis constructed by optimization to prevent leakage out of the regions of interest, we use robust signal processing and statistical estimation methods. Applying those to the latest time series of monthly GRACE solutions we map Antarctica's mass loss in space and time as well as can be recovered from satellite gravity alone. Ignoring GIA model uncertainty, over the period 2003-2014, West Antarctica has been losing ice mass at a rate of - 121 ± 8 Gt /yr and has experienced large acceleration of ice mass losses along the Amundsen Sea coast of - 18 ± 5 Gt /yr2, doubling the mass loss rate in the past six years. The Antarctic Peninsula shows slightly accelerating ice mass loss, with larger accelerated losses in the southern half of the Peninsula. Ice mass gains due to snowfall in Dronning Maud Land have continued to add about half the amount of West Antarctica's loss back onto the continent over the last decade. We estimate the overall mass losses from Antarctica since January 2003 at - 92 ± 10 Gt /yr.

  10. Mass Gains of the Antarctic Ice Sheet Exceed Losses

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David

    2012-01-01

    During 2003 to 2008, the mass gain of the Antarctic ice sheet from snow accumulation exceeded the mass loss from ice discharge by 49 Gt/yr (2.5% of input), as derived from ICESat laser measurements of elevation change. The net gain (86 Gt/yr) over the West Antarctic (WA) and East Antarctic ice sheets (WA and EA) is essentially unchanged from revised results for 1992 to 2001 from ERS radar altimetry. Imbalances in individual drainage systems (DS) are large (-68% to +103% of input), as are temporal changes (-39% to +44%). The recent 90 Gt/yr loss from three DS (Pine Island, Thwaites-Smith, and Marie-Bryd Coast) of WA exceeds the earlier 61 Gt/yr loss, consistent with reports of accelerating ice flow and dynamic thinning. Similarly, the recent 24 Gt/yr loss from three DS in the Antarctic Peninsula (AP) is consistent with glacier accelerations following breakup of the Larsen B and other ice shelves. In contrast, net increases in the five other DS of WA and AP and three of the 16 DS in East Antarctica (EA) exceed the increased losses. Alternate interpretations of the mass changes driven by accumulation variations are given using results from atmospheric-model re-analysis and a parameterization based on 5% change in accumulation per degree of observed surface temperature change. A slow increase in snowfall with climate waRMing, consistent with model predictions, may be offsetting increased dynamic losses.

  11. Greenland Ice Sheet Surface Temperature, Melt, and Mass Loss: 2000-2006

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo

    2007-01-01

    Extensive melt on the Greenland Ice Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland Ice Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the ice sheet will increase melt by 20-50% therefore, surface temperature is one of the most important ice-sheet parameters to study for analysis of changes in the mass balance of the ice-sheet. The Greenland Ice Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the ice were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the ice-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland Ice Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in mass of the ice sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of ice-sheet mass loss and gain.

  12. Thickening and Thinning of Antarctic Ice Shelves and Tongues and Mass Balance Estimates

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Giovinetto, Mario; Robbins, John; Saba, Jack L.; Yi, Donghui

    2011-01-01

    Previous analysis of elevation changes for 1992 to 2002 obtained from measurements by radar altimeters on ERS-l and 2 showed that the shelves in the Antarctic Peninsula (AP) and along the coast of West Antarctica (WA), including the eastern part of the Ross Ice Shelf, were mostly thinning and losing mass whereas the Ronne Ice shelf also in WA was mostly thickening. The estimated total mass loss for the floating ice shelves and ice tongues from ice draining WA and the AP was 95 Gt/a. In contrast, the floating ice shelves and ice tongues from ice draining East Antarctica (EA), including the Filchner, Fimbul, Amery, and Western Ross, were mostly thickening with a total estimated mass gain of 142 Gt/a. Data from ICESat laser altimetry for 2003-2008 gives new surface elevation changes (dH/dt) with some similar values for the earlier and latter periods, including -27.6 and -26.9 cm a-Ion the West Getz ice shelf and -42.4 and - 27.2 cm/a on the East Getz ice shelf, and some values that indicate more thinning in the latter period, including -17.9 and -36.2 cm/a on the Larsen C ice shelf, -35.5 and -76.0 cm/a on the Pine Island Glacier floating, -60.5 and -125.7 .cm/a on the Smith Glacier floating, and -34.4 and -108.9 cm/a on the Thwaites Glacier floating. Maps of measured dH/dt and estimated thickness change are produced along with mass change estimates for 2003 - 2008.

  13. Mass Balance of the West Antarctic Ice-Sheet from ICESat Measurements

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Robins, John; Saba, Jack L.; Yi, Donghui

    2011-01-01

    Mass balance estimates for 2003-2008 are derived from ICESat laser altimetry and compared with estimates for 1992-2002 derived from ERS radar altimetry. The net mass balance of 3 drainage systems (Pine Island, Thwaites/Smith, and the coast of Marie Bryd) for 2003-2008 is a loss of 100 Gt/yr, which increased from a loss of 70 Gt/yr for the earlier period. The DS including the Bindschadler and MacAyeal ice streams draining into the Ross Ice Shelf has a mass gain of 11 Gt/yr for 2003-2008, compared to an earlier loss of 70 Gt/yr. The DS including the Whillans and Kamb ice streams has a mass gain of 12 Gt/yr, including a significant thickening on the upper part of the Kamb DS, compared to a earlier gain of 6 Gt/yr (includes interpolation for a large portion of the DS). The other two DS discharging into the Ronne Ice Shelf and the northern Ellsworth Coast have a mass gain of 39 Gt/yr, compared to a gain of 4 Gt/yr for the earlier period. Overall, the increased losses of 30 Gt/yr in the Pine Island, Thwaites/Smith, and the coast of Marie Bryd DSs are exceeded by increased gains of 59 Gt/yr in the other 4 DS. Overall, the mass loss from the West Antarctic ice sheet has decreased to 38 Gt/yr from the earlier loss of 67 Gt/yr, reducing the contribution to sea level rise to 0.11 mm/yr from 0.19 mm/yr

  14. Determination of Interannual to Decadal Changes in Ice Sheet Mass Balance from Satellite Altimetry

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Busalacchi, Antonioa J. (Technical Monitor)

    2001-01-01

    A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the +/- 25% uncertainty in current mass balance corresponds to +/- 2 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. Although the overall ice mass balance and seasonal and inter-annual variations can be derived from time-series of ice surface elevations from satellite altimetry, satellite radar altimeters have been limited in spatial coverage and elevation accuracy. Nevertheless, new data analysis shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. In addition, observed seasonal and interannual variations in elevation demonstrate the potential for relating the variability in mass balance to changes in precipitation, temperature, and melting. From 2001, NASA's ICESat laser altimeter mission will provide significantly better elevation accuracy and spatial coverage to 86 deg latitude and to the margins of the ice sheets. During 3 to 5 years of ICESat-1 operation, an estimate of the overall ice sheet mass balance and sea level contribution will be obtained. The importance of continued ice monitoring after the first ICESat is illustrated by the variability in the area of Greenland surface melt observed over 17-years and its correlation with temperature. In addition, measurement of ice sheet changes, along with measurements of sea level change by a series of ocean altimeters, should enable direct detection of ice level and global sea level correlations.

  15. Glacier Ice Mass Fluctuations and Fault Instability in Tectonically Active Southern Alaska

    NASA Technical Reports Server (NTRS)

    SauberRosenberg, Jeanne M.; Molnia, Bruce F.

    2003-01-01

    Across southern Alaska the northwest directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. This has led to high tectonic strain rates and dramatic topographic relief of more than 5000 meters within 15 km of the Gulf of Alaska coast. The glaciers of this area are extensive and include large glaciers undergoing wastage (glacier retreat and thinning) and surges. The large glacier ice mass changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with ice mass fluctuations and tectonic loading by examining GPS geodetic observations and numerical model predictions. Although the glacial fluctuations perturb the tectonic stress field, especially at shallow depths, the largest contribution to ongoing crustal deformation is horizontal tectonic strain due to plate convergence. Tectonic forces are thus the primary force responsible for major earthquakes. However, for geodetic sites located < 10-20 km from major ice mass fluctuations, the changes of the solid Earth due to ice loading and unloading are an important aspect of interpreting geodetic results. The ice changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, ice mass fluctuations associated with the surge cycle can modify the short-term seismicity rates in a local region. For the thrust faulting environment of the study region a large decrease in ice load may cause an increase in seismic rate in a region close to failure whereas ice loading may inhibit thrust faulting.

  16. Mass Balance Changes and Ice Dynamics of Greenland and Antarctic Ice Sheets from Laser Altimetry

    NASA Astrophysics Data System (ADS)

    Babonis, G. S.; Csatho, B.; Schenk, T.

    2016-06-01

    During the past few decades the Greenland and Antarctic ice sheets have lost ice at accelerating rates, caused by increasing surface temperature. The melting of the two big ice sheets has a big impact on global sea level rise. If the ice sheets would melt down entirely, the sea level would rise more than 60 m. Even a much smaller rise would cause dramatic damage along coastal regions. In this paper we report about a major upgrade of surface elevation changes derived from laser altimetry data, acquired by NASA's Ice, Cloud and land Elevation Satellite mission (ICESat) and airborne laser campaigns, such as Airborne Topographic Mapper (ATM) and Land, Vegetation and Ice Sensor (LVIS). For detecting changes in ice sheet elevations we have developed the Surface Elevation Reconstruction And Change detection (SERAC) method. It computes elevation changes of small surface patches by keeping the surface shape constant and considering the absolute values as surface elevations. We report about important upgrades of earlier results, for example the inclusion of local ice caps and the temporal extension from 1993 to 2014 for the Greenland Ice Sheet and for a comprehensive reconstruction of ice thickness and mass changes for the Antarctic Ice Sheets.

  17. Prediction of dry ice mass for firefighting robot actuation

    NASA Astrophysics Data System (ADS)

    Ajala, M. T.; Khan, Md R.; Shafie, A. A.; Salami, MJE; Mohamad Nor, M. I.

    2017-11-01

    The limitation in the performance of electric actuated firefighting robots in high-temperature fire environment has led to research on the alternative propulsion system for the mobility of firefighting robots in such environment. Capitalizing on the limitations of these electric actuators we suggested a gas-actuated propulsion system in our earlier study. The propulsion system is made up of a pneumatic motor as the actuator (for the robot) and carbon dioxide gas (self-generated from dry ice) as the power source. To satisfy the consumption requirement (9cfm) of the motor for efficient actuation of the robot in the fire environment, the volume of carbon dioxide gas, as well as the corresponding mass of the dry ice that will produce the required volume for powering and actuation of the robot, must be determined. This article, therefore, presents the computational analysis to predict the volumetric requirement and the dry ice mass sufficient to power a carbon dioxide gas propelled autonomous firefighting robot in a high-temperature environment. The governing equation of the sublimation of dry ice to carbon dioxide is established. An operating time of 2105.53s and operating pressure ranges from 137.9kPa to 482.65kPa were achieved following the consumption rate of the motor. Thus, 8.85m3 is computed as the volume requirement of the CAFFR while the corresponding dry ice mass for the CAFFR actuation ranges from 21.67kg to 75.83kg depending on the operating pressure.

  18. Estimates of Ice Sheet Mass Balance from Satellite Altimetry: Past and Future

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the 20% uncertainty in current mass balance corresponds to 1.6 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. A principal purpose of obtaining ice sheet elevation changes from satellite altimetry has been estimation of the current ice sheet mass balance. Limited information on ice sheet elevation change and their implications about mass balance have been reported by several investigators from radar altimetry (Seasat, Geosat, ERS-1&2). Analysis of ERS-1&2 data over Greenland for 7 years from 1992 to 1999 shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. Observed seasonal and interannual variations in ice surface elevation are larger than previously expected because of seasonal and interannUal variations in precipitation, melting, and firn compaction. In the accumulation zone, the variations in firn compaction are modeled as a function of temperature leaving variations in precipitation and the mass balance trend. Significant interannual variations in elevation in some locations, in particular the difference in trends from 1992 to 1995 compared to 1995 to 1999, can be explained by changes in precipitation over Greenland. Over the 7 years, trends in elevation are mostly positive at higher elevations and negative at lower elevations. In addition, trends for the winter seasons (from a trend analysis through the average winter elevations) are more positive than the corresponding trends for the summer. At lower elevations, the 7-year trends in some locations are strongly negative for summer and near zero or slightly positive for winter. These

  19. A Multi-Moment Bulkwater Ice Microphysics Scheme with Consideration of the Adaptive Growth Habit and Apparent Density for Pristine Ice in the WRF Model

    NASA Astrophysics Data System (ADS)

    Tsai, T. C.; Chen, J. P.; Dearden, C.

    2014-12-01

    The wide variety of ice crystal shapes and growth habits makes it a complicated issue in cloud models. This study developed the bulk ice adaptive habit parameterization based on the theoretical approach of Chen and Lamb (1994) and introduced a 6-class hydrometeors double-moment (mass and number) bulk microphysics scheme with gamma-type size distribution function. Both the proposed schemes have been implemented into the Weather Research and Forecasting model (WRF) model forming a new multi-moment bulk microphysics scheme. Two new moments of ice crystal shape and volume are included for tracking pristine ice's adaptive habit and apparent density. A closure technique is developed to solve the time evolution of the bulk moments. For the verification of the bulk ice habit parameterization, some parcel-type (zero-dimension) calculations were conducted and compared with binned numerical calculations. The results showed that: a flexible size spectrum is important in numerical accuracy, the ice shape can significantly enhance the diffusional growth, and it is important to consider the memory of growth habit (adaptive growth) under varying environmental conditions. Also, the derived results with the 3-moment method were much closer to the binned calculations. A field campaign of DIAMET was selected to simulate in the WRF model for real-case studies. The simulations were performed with the traditional spherical ice and the new adaptive shape schemes to evaluate the effect of crystal habits. Some main features of narrow rain band, as well as the embedded precipitation cells, in the cold front case were well captured by the model. Furthermore, the simulations produced a good agreement in the microphysics against the aircraft observations in ice particle number concentration, ice crystal aspect ratio, and deposition heating rate especially within the temperature region of ice secondary multiplication production.

  20. Winter mass balance of Drangajökull ice cap (NW Iceland) derived from satellite sub-meter stereo images

    NASA Astrophysics Data System (ADS)

    Belart, Joaquín M. C.; Berthier, Etienne; Magnússon, Eyjólfur; Anderson, Leif S.; Pálsson, Finnur; Thorsteinsson, Thorsteinn; Howat, Ian M.; Aðalgeirsdóttir, Guðfinna; Jóhannesson, Tómas; Jarosch, Alexander H.

    2017-06-01

    Sub-meter resolution, stereoscopic satellite images allow for the generation of accurate and high-resolution digital elevation models (DEMs) over glaciers and ice caps. Here, repeated stereo images of Drangajökull ice cap (NW Iceland) from Pléiades and WorldView2 (WV2) are combined with in situ estimates of snow density and densification of firn and fresh snow to provide the first estimates of the glacier-wide geodetic winter mass balance obtained from satellite imagery. Statistics in snow- and ice-free areas reveal similar vertical relative accuracy (< 0.5 m) with and without ground control points (GCPs), demonstrating the capability for measuring seasonal snow accumulation. The calculated winter (14 October 2014 to 22 May 2015) mass balance of Drangajökull was 3.33 ± 0.23 m w.e. (meter water equivalent), with ∼ 60 % of the accumulation occurring by February, which is in good agreement with nearby ground observations. On average, the repeated DEMs yield 22 % less elevation change than the length of eight winter snow cores due to (1) the time difference between in situ and satellite observations, (2) firn densification and (3) elevation changes due to ice dynamics. The contributions of these three factors were of similar magnitude. This study demonstrates that seasonal geodetic mass balance can, in many areas, be estimated from sub-meter resolution satellite stereo images.

  1. Communication: Disorder-suppressed vibrational relaxation in vapor-deposited high-density amorphous ice

    NASA Astrophysics Data System (ADS)

    Shalit, Andrey; Perakis, Fivos; Hamm, Peter

    2014-04-01

    We apply two-dimensional infrared spectroscopy to differentiate between the two polyamorphous forms of glassy water, low-density (LDA) and high-density (HDA) amorphous ices, that were obtained by slow vapor deposition at 80 and 11 K, respectively. Both the vibrational lifetime and the bandwidth of the 1-2 transition of the isolated OD stretch vibration of HDO in H2O exhibit characteristic differences when comparing hexagonal (Ih), LDA, and HDA ices, which we attribute to the different local structures - in particular the presence of interstitial waters in HDA ice - that cause different delocalization lengths of intermolecular phonon degrees of freedom. Moreover, temperature dependent measurements show that the vibrational lifetime closely follows the structural transition between HDA and LDA phases.

  2. The influence of topographic feedback on a coupled mass balance and ice-flow model for Vestfonna ice-cap, Svalbard

    NASA Astrophysics Data System (ADS)

    Schäfer, Martina; Möller, Marco; Zwinger, Thomas; Moore, John

    2016-04-01

    Using a coupled simulation set-up between a by statistical climate data forced and to ice-cap resolution downscaled mass balance model and an ice-dynamic model, we study coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analysing the impacts of different imposed coupling intervals on mass-balance and sea-level rise (SLR) projections. Based on a method to estimate errors introduced by different coupling schemes, we find that neglecting the topographic feedback in the coupling leads to underestimations of 10-20% in SLR projections on century time-scales in our model compared to full coupling (i.e., exchange of properties using smallest occurring time-step). Using the same method it also is shown that parametrising mass-balance adjustment for changes in topography using lapse rates is a - in computational terms - cost-effective reasonably accurate alternative applied to an ice-cap like Vestfonna. We test the forcing imposed by different emission pathways (RCP 2.4, 4.5, 6.0 and 8.5). For most of them, over the time-period explored (2000-2100), fast-flowing outlet glaciers decrease in impacting SLR due to their deceleration and reduced mass flux as they thin and retreat from the coast, hence detaching from the ocean and thereby losing their major mass drainage mechanism, i.e., calving.

  3. Antarctic ice sheet mass loss estimates using Modified Antarctic Mapping Mission surface flow observations

    NASA Astrophysics Data System (ADS)

    Ren, Diandong; Leslie, Lance M.; Lynch, Mervyn J.

    2013-03-01

    The long residence time of ice and the relatively gentle slopes of the Antarctica Ice Sheet make basal sliding a unique positive feedback mechanism in enhancing ice discharge along preferred routes. The highly organized ice stream channels extending to the interior from the lower reach of the outlets are a manifestation of the role of basal granular material in enhancing the ice flow. In this study, constraining the model-simulated year 2000 ice flow fields with surface velocities obtained from InSAR measurements permits retrieval of the basal sliding parameters. Forward integrations of the ice model driven by atmospheric and oceanic parameters from coupled general circulation models under different emission scenarios provide a range of estimates of total ice mass loss during the 21st century. The total mass loss rate has a small intermodel and interscenario spread, rising from approximately -160 km3/yr at present to approximately -220 km3/yr by 2100. The accelerated mass loss rate of the Antarctica Ice Sheet in a warming climate is due primarily to a dynamic response in the form of an increase in ice flow speed. Ice shelves contribute to this feedback through a reduced buttressing effect due to more frequent systematic, tabular calving events. For example, by 2100 the Ross Ice Shelf is projected to shed 40 km3 during each systematic tabular calving. After the frontal section's attrition, the remaining shelf will rebound. Consequently, the submerged cross-sectional area will reduce, as will the buttressing stress. Longitudinal differential warming of ocean temperature contributes to tabular calving. Because of the prevalence of fringe ice shelves, oceanic effects likely will play a very important role in the future mass balance of the Antarctica Ice Sheet, under a possible future warming climate.

  4. Atypical water lattices and their possible relevance to the amorphous ices: A density functional study

    NASA Astrophysics Data System (ADS)

    Anick, David J.

    2013-04-01

    Of the fifteen known crystalline forms of ice, eleven consist of a single topologically connected hydrogen bond network with four H-bonds at every O. The other four, Ices VI-VIII and XV, consist of two topologically connected networks, each with four H-bonds at every O. The networks interpenetrate but do not share H-bonds. This article presents two new periodic water lattice families whose topological connectivity is "atypical": they consist of many two-dimensional layers that share no H-bonds. Layers are held together only by dispersion forces. Within each layer there are still four H-bonds at each O. Called "Hexagonal Bilayer Water" (HBW) and "Pleated Sheet Water" (PSW), they have computed densities of about 1.1 g/mL and 1.3 g/mL respectively, and nearest neighbor O-coordination is 4.5 to 5.5 and 6 to 8 respectively. Using density functional theory (BLYP-D/TZVP), various proton ordered forms of HBW and PSW are optimized and categorized. There are simple pathways connecting Ice-Ih to HBW and HBW to PSW. Their computed properties suggest similarities to the high density and very high density amorphous ices (HDA and VHDA) respectively. It is unknown whether HDA, VHDA, and Low Density Amorphous Ice (LDA) are fully disordered glasses down to the molecular level, or whether there is some short-range local order. Based on estimated radial distribution functions (RDFs), one proton ordered form of HBW matches HDA best. The idea is explored that HDA could contain islands with this underlying structure, and likewise, that VHDA could contain regions of PSW. A "microlattice model version 1" (MLM1) is presented as a device to compare key experimental data on the amorphous ices with these atypical structures and with a microlattice form of Ice-XI for LDA. Resemblances are found with the amorphs' RDFs, densities, Raman spectra, and transition behaviors. There is not enough information in the static models to assign either a microlattice structure or a partial microlattice

  5. Is snow-ice now a major contributor to sea ice mass balance in the western Transpolar Drift region?

    NASA Astrophysics Data System (ADS)

    Graham, R. M.; Merkouriadi, I.; Cheng, B.; Rösel, A.; Granskog, M. A.

    2017-12-01

    During the Norwegian young sea ICE (N-ICE2015) campaign, which took place in the first half of 2015 north of Svalbard, a deep winter snow pack (50 cm) on sea ice was observed, that was 50% thicker than earlier climatological studies suggested for this region. Moreover, a significant fraction of snow contributed to the total ice mass in second-year ice (SYI) (9% on average). Interestingly, very little snow (3% snow by mass) was present in first-year ice (FYI). The combination of sea ice thinning and increased precipitation north of Svalbard is expected to promote the formation of snow-ice. Here we use the 1-D snow/ice thermodynamic model HIGHTSI forced with reanalysis data, to show that for the case study of N-ICE2015, snow-ice would even form over SYI with an initial thickness of 2 m. In current conditions north of Svalbard, snow-ice is ubiquitous and contributes to the thickness growth up to 30%. This contribution is important, especially in the absence of any bottom thermodynamic growth due to the thick insulating snow cover. Growth of FYI north of Svalbard is mainly controlled by the timing of growth onset relative to snow precipitation events and cold spells. These usually short-lived conditions are largely determined by the frequency of storms entering the Arctic from the Atlantic Ocean. In our case, a later freeze onset was favorable for FYI growth due to less snow accumulation in early autumn. This limited snow-ice formation but promoted bottom thermodynamic growth. We surmise these findings are related to a regional phenomenon in the Atlantic sector of the Arctic, with frequent storm events which bring increasing amounts of precipitation in autumn and winter, and also affect the duration of cold temperatures required for ice growth in winter. We discuss the implications for the importance of snow-ice in the future Arctic, formerly believed to be non-existent in the central Arctic due to thick perennial ice.

  6. Forces Generated by High Velocity Impact of Ice on a Rigid Structure

    NASA Technical Reports Server (NTRS)

    Pereira, J. Michael; Padula, Santo A., II; Revilock, Duane M.; Melis, Matthew E.

    2006-01-01

    Tests were conducted to measure the impact forces generated by cylindrical ice projectiles striking a relatively rigid target. Two types of ice projectiles were used, solid clear ice and lower density fabricated ice. Three forms of solid clear ice were tested: single crystal, poly-crystal, and "rejected" poly-crystal (poly-crystal ice in which defects were detected during inspection.) The solid ice had a density of approximately 56 lb/cu ft (0.9 gm/cu cm). A second set of test specimens, termed "low density ice" was manufactured by molding shaved ice into a cylindrical die to produce ice with a density of approximately 40 lb/cu ft (0.65 gm/cu cm). Both the static mechanical characteristics and the crystalline structure of the ice were found to have little effect on the observed transient response. The impact forces generated by low density ice projectiles, which had very low mechanical strength, were comparable to those of full density solid ice. This supports the hypothesis that at a velocity significantly greater than that required to produce fracture in the ice, the mechanical properties become relatively insignificant, and the impact forces are governed by the shape and mass of the projectile.

  7. Toward Surface Mass Balance Modeling over Antarctic Peninsula with Improved Snow/Ice Physics within WRF

    NASA Astrophysics Data System (ADS)

    Villamil-Otero, G.; Zhang, J.; Yao, Y.

    2017-12-01

    The Antarctic Peninsula (AP) has long been the focus of climate change studies due to its rapid environmental changes such as significantly increased glacier melt and retreat, and ice-shelf break-up. Progress has been continuously made in the use of regional modeling to simulate surface mass changes over ice sheets. Most efforts, however, focus on the ice sheets of Greenland with considerable fewer studies in Antarctica. In this study the Weather Research and Forecasting (WRF) model, which has been applied to the Antarctic region for weather modeling, is adopted to capture the past and future surface mass balance changes over AP. In order to enhance the capabilities of WRF model simulating surface mass balance over the ice surface, we implement various ice and snow processes within the WRF and develop a new WRF suite (WRF-Ice). The WRF-Ice includes a thermodynamic ice sheet model that improves the representation of internal melting and refreezing processes and the thermodynamic effects over ice sheet. WRF-Ice also couples a thermodynamic sea ice model to improve the simulation of surface temperature and fluxes over sea ice. Lastly, complex snow processes are also taken into consideration including the implementation of a snowdrift model that takes into account the redistribution of blowing snow as well as the thermodynamic impact of drifting snow sublimation on the lower atmospheric boundary layer. Intensive testing of these ice and snow processes are performed to assess the capability of WRF-Ice in simulating the surface mass balance changes over AP.

  8. Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Powell, Diana; Murray-Clay, Ruth; Schlichting, Hilke E.

    2017-05-01

    We present a novel method for determining the surface density of protoplanetary disks through consideration of disk “dust lines,” which indicate the observed disk radial scale at different observational wavelengths. This method relies on the assumption that the processes of particle growth and drift control the radial scale of the disk at late stages of disk evolution such that the lifetime of the disk is equal to both the drift timescale and growth timescale of the maximum particle size at a given dust line. We provide an initial proof of concept of our model through an application to the disk TW Hya and are able to estimate the disk dust-to-gas ratio, CO abundance, and accretion rate in addition to the total disk surface density. We find that our derived surface density profile and dust-to-gas ratio are consistent with the lower limits found through measurements of HD gas. The CO ice line also depends on surface density through grain adsorption rates and drift and we find that our theoretical CO ice line estimates have clear observational analogues. We further apply our model to a large parameter space of theoretical disks and find three observational diagnostics that may be used to test its validity. First, we predict that the dust lines of disks other than TW Hya will be consistent with the normalized CO surface density profile shape for those disks. Second, surface density profiles that we derive from disk ice lines should match those derived from disk dust lines. Finally, we predict that disk dust and ice lines will scale oppositely, as a function of surface density, across a large sample of disks.

  9. Insight into glacier climate interaction: reconstruction of the mass balance field using ice extent data

    NASA Astrophysics Data System (ADS)

    Visnjevic, Vjeran; Herman, Frédéric; Licul, Aleksandar

    2016-04-01

    With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. We recently developed a model that describes large-scale erosion and its response to climate and dynamical changes with the application to the Alps for the LGM period. Here we will present an inverse approach we have recently developed to infer the LGM mass balance from known ice extent data, focusing on a glacier or ice cap. The ice flow model is developed using the shallow ice approximation and the developed codes are accelerated using GPUs capabilities. The mass balance field is the constrained variable defined by the balance rate β and the equilibrium line altitude (ELA), where c is the cutoff value: b = max(βṡ(S(z) - ELA), c) We show that such a mass balance can be constrained from the observed past ice extent and ice thickness. We are also investigating several different geostatistical methods to constrain spatially variable mass balance, and derive uncertainties on each of the mass balance parameters.

  10. Present-day Antarctic ice mass changes and crustal motion

    NASA Technical Reports Server (NTRS)

    James, Thomas S.; Ivins, Erik R.

    1995-01-01

    The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic ice sheet mass balance are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak Antarctic vertical velocities of the ICE-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene Antarctic deglaciation history protrayed in ICE-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(exp 21) Pa(dot)s, then a vast geographical region in West Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean mass exchange is large enough to account for a substantial portion of the observed secular polar motion (omega m(arrow dot)) and time-varying zonal gravity field.

  11. Present-day Antarctic Ice Mass Changes and Crustal Motion

    NASA Technical Reports Server (NTRS)

    James, Thomas S.; Ivins, Erik R.

    1995-01-01

    The peak vertical velocities predicted by three realistic, but contrasting, present-day scenarios of Antarctic ice sheet mass balance are found to be of the order of several mm/a. One scenario predicts local uplift rates in excess of 5 mm/a. These rates are small compared to the peak Antarctic vertical velocities of the ICE-3G glacial rebound model, which are in excess of 20 mm/a. If the Holocene Antarctic deglaciation history portrayed in ICE-3G is realistic, and if regional upper mantle viscosity is not an order of magnitude below 10(exp 21) pa s, then a vast geographical region in West Antarctica is uplifting at a rate that could be detected by a future Global Positioning System (GPS) campaign. While present-day scenarios predict small vertical crustal velocities, their overall continent-ocean mass exchange is large enough to account for a substantial portion of the observed secular polar motion ((Omega)m(bar)) and time-varying zonal gravity field J(sub 1).

  12. Non-basal dislocations should be accounted for in simulating ice mass flow

    NASA Astrophysics Data System (ADS)

    Chauve, T.; Montagnat, M.; Piazolo, S.; Journaux, B.; Wheeler, J.; Barou, F.; Mainprice, D.; Tommasi, A.

    2017-09-01

    Prediction of ice mass flow and associated dynamics is pivotal at a time of climate change. Ice flow is dominantly accommodated by the motion of crystal defects - the dislocations. In the specific case of ice, their observation is not always accessible by means of the classical tools such as X-ray diffraction or transmission electron microscopy (TEM). Part of the dislocation population, the geometrically necessary dislocations (GNDs) can nevertheless be constrained using crystal orientation measurements via electron backscattering diffraction (EBSD) associated with appropriate analyses based on the Nye (1950) approach. The present study uses the Weighted Burgers Vectors, a reduced formulation of the Nye theory that enables the characterization of GNDs. Applied to ice, this method documents, for the first time, the presence of dislocations with non-basal [ c ] or < c + a > Burgers vectors. These [ c ] or < c + a > dislocations represent up to 35% of the GNDs observed in laboratory-deformed ice samples. Our findings offer a more complex and comprehensive picture of the key plasticity processes responsible for polycrystalline ice creep and provide better constraints on the constitutive mechanical laws implemented in ice sheet flow models used to predict the response of Earth ice masses to climate change.

  13. Land motion due to 20th century mass balance of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Kjeldsen, K. K.; Khan, S. A.

    2017-12-01

    Quantifying the contribution from ice sheets and glaciers to past sea level change is of great value for understanding sea level projections into the 21st century. However, quantifying and understanding past changes are equally important, in particular understanding the impact in the near-field where the signal is highest. We assess the impact of 20th century mass balance of the Greenland Ice Sheet on land motion using results from Kjeldsen et al, 2015. These results suggest that the ice sheet on average lost a minimum of 75 Gt/yr, but also show that the mass balance was highly spatial- and temporal variable, and moreover that on a centennial time scale changes were driven by a decreasing surface mass balance. Based on preliminary results we discuss land motion during the 20th century due to mass balance changes and the driving components surface mass balance and ice dynamics.

  14. Bedrock displacements in Greenland manifest ice mass variations, climate cycles and climate change

    PubMed Central

    Bevis, Michael; Wahr, John; Khan, Shfaqat A.; Madsen, Finn Bo; Brown, Abel; Willis, Michael; Kendrick, Eric; Knudsen, Per; Box, Jason E.; van Dam, Tonie; Caccamise, Dana J.; Johns, Bjorn; Nylen, Thomas; Abbott, Robin; White, Seth; Miner, Jeremy; Forsberg, Rene; Zhou, Hao; Wang, Jian; Wilson, Terry; Bromwich, David; Francis, Olivier

    2012-01-01

    The Greenland GPS Network (GNET) uses the Global Positioning System (GPS) to measure the displacement of bedrock exposed near the margins of the Greenland ice sheet. The entire network is uplifting in response to past and present-day changes in ice mass. Crustal displacement is largely accounted for by an annual oscillation superimposed on a sustained trend. The oscillation is driven by earth’s elastic response to seasonal variations in ice mass and air mass (i.e., atmospheric pressure). Observed vertical velocities are higher and often much higher than predicted rates of postglacial rebound (PGR), implying that uplift is usually dominated by the solid earth’s instantaneous elastic response to contemporary losses in ice mass rather than PGR. Superimposed on longer-term trends, an anomalous ‘pulse’ of uplift accumulated at many GNET stations during an approximate six-month period in 2010. This anomalous uplift is spatially correlated with the 2010 melting day anomaly. PMID:22786931

  15. Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

    NASA Astrophysics Data System (ADS)

    Sauber, Jeanne M.; Molnia, Bruce F.

    2004-07-01

    Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes ( ML≥2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes ( Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake ( Ms=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass

  16. Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

    USGS Publications Warehouse

    Sauber, J.M.; Molnia, B.F.

    2004-01-01

    Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes (ML???2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes (Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake (M s=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass

  17. Geodetic glacier mass balancing on ice caps - inseparably connected to firn modelling?

    NASA Astrophysics Data System (ADS)

    Saß, Björn L.; Sauter, Tobias; Seehaus, Thorsten; Braun, Matthias H.

    2017-04-01

    Observed melting of glaciers and ice caps in the polar regions contribute to the ongoing global sea level rise (SLR). A rising sea level and its consequences are one of the major challenges for coastal societies in the next decades to centuries. Gaining knowledge about the main drivers of SLR and bringing it together is one recent key-challenge for environmental science. The high arctic Svalbard archipelago faced a strong climatic change in the last decades, associated with a change in the cryosphere. Vestfonna, a major Arctic ice cap in the north east of Svalbard, harbors land and marine terminating glaciers, which expose a variability of behavior. We use high resolution remote sensing data from space-borne radar (TanDEM-X, TerraSAR-X, Sentinel-1a), acquired between 2009 and 2015, to estimate glacier velocity and high accurate surface elevation changes. For DEM registration we use space-borne laser altimetry (ICESat) and an existing in-situ data archive (IPY Kinnvika). In order to separate individual glacier basin changes for a detailed mass balance study and for further SLR contribution estimates, we use glacier outlines from the Global Land Ice Measurements from Space (GLIMS) project. Remaining challenges of space-borne observations are the reduction of measurement uncertainties, in the case of Synthetic Aperture Radar most notably signal penetration into the glacier surface. Furthermore, in order to convert volume to mass change one has to use the density of the changed mass (conversion factor) and one has to account for the mass conservation processes in the firn package (firn compaction). Both, the conversion factor and the firn compaction are not (yet) measurable for extensive ice bodies. They have to be modelled by coupling point measurements and regional gridded climate data. Results indicate a slight interior thickening contrasted with wide spread thinning in the ablation zone of the marine terminating outlets. While one glacier system draining to the

  18. Surface water mass composition changes captured by cores of Arctic land-fast sea ice

    NASA Astrophysics Data System (ADS)

    Smith, I. J.; Eicken, H.; Mahoney, A. R.; Van Hale, R.; Gough, A. J.; Fukamachi, Y.; Jones, J.

    2016-04-01

    In the Arctic, land-fast sea ice growth can be influenced by fresher water from rivers and residual summer melt. This paper examines a method to reconstruct changes in water masses using oxygen isotope measurements of sea ice cores. To determine changes in sea water isotope composition over the course of the ice growth period, the output of a sea ice thermodynamic model (driven with reanalysis data, observations of snow depth, and freeze-up dates) is used along with sea ice oxygen isotope measurements and an isotopic fractionation model. Direct measurements of sea ice growth rates are used to validate the output of the sea ice growth model. It is shown that for sea ice formed during the 2011/2012 ice growth season at Barrow, Alaska, large changes in isotopic composition of the ocean waters were captured by the sea ice isotopic composition. Salinity anomalies in the ocean were also tracked by moored instruments. These data indicate episodic advection of meteoric water, having both lower salinity and lower oxygen isotopic composition, during the winter sea ice growth season. Such advection of meteoric water during winter is surprising, as no surface meltwater and no local river discharge should be occurring at this time of year in that area. How accurately changes in water masses as indicated by oxygen isotope composition can be reconstructed using oxygen isotope analysis of sea ice cores is addressed, along with methods/strategies that could be used to further optimize the results. The method described will be useful for winter detection of meteoric water presence in Arctic fast ice regions, which is important for climate studies in a rapidly changing Arctic. Land-fast sea ice effective fractionation coefficients were derived, with a range of +1.82‰ to +2.52‰. Those derived effective fractionation coefficients will be useful for future water mass component proportion calculations. In particular, the equations given can be used to inform choices made when

  19. Insights into Spatial Sensitivities of Ice Mass Response to Environmental Change from the SeaRISE Ice Sheet Modeling Project I: Antarctica

    NASA Technical Reports Server (NTRS)

    Nowicki, Sophie; Bindschadler, Robert A.; Abe-Ouchi, Ayako; Aschwanden, Andy; Bueler, Ed; Choi, Hyengu; Fastook, Jim; Granzow, Glen; Greve, Ralf; Gutowski, Gail; hide

    2013-01-01

    Atmospheric, oceanic, and subglacial forcing scenarios from the Sea-level Response to Ice Sheet Evolution (SeaRISE) project are applied to six three-dimensional thermomechanical ice-sheet models to assess Antarctic ice sheet sensitivity over a 500 year timescale and to inform future modeling and field studies. Results indicate (i) growth with warming, except within low-latitude basins (where inland thickening is outpaced by marginal thinning); (ii) mass loss with enhanced sliding (with basins dominated by high driving stresses affected more than basins with low-surface-slope streaming ice); and (iii) mass loss with enhanced ice shelf melting (with changes in West Antarctica dominating the signal due to its marine setting and extensive ice shelves; cf. minimal impact in the Terre Adelie, George V, Oates, and Victoria Land region of East Antarctica). Ice loss due to dynamic changes associated with enhanced sliding and/or sub-shelf melting exceeds the gain due to increased precipitation. Furthermore, differences in results between and within basins as well as the controlling impact of sub-shelf melting on ice dynamics highlight the need for improved understanding of basal conditions, grounding-zone processes, ocean-ice interactions, and the numerical representation of all three.

  20. A new temperature- and humidity-dependent surface site density approach for deposition ice nucleation

    NASA Astrophysics Data System (ADS)

    Steinke, I.; Hoose, C.; Möhler, O.; Connolly, P.; Leisner, T.

    2015-04-01

    Deposition nucleation experiments with Arizona Test Dust (ATD) as a surrogate for mineral dusts were conducted at the AIDA cloud chamber at temperatures between 220 and 250 K. The influence of the aerosol size distribution and the cooling rate on the ice nucleation efficiencies was investigated. Ice nucleation active surface site (INAS) densities were calculated to quantify the ice nucleation efficiency as a function of temperature, humidity and the aerosol surface area concentration. Additionally, a contact angle parameterization according to classical nucleation theory was fitted to the experimental data in order to relate the ice nucleation efficiencies to contact angle distributions. From this study it can be concluded that the INAS density formulation is a very useful tool to describe the temperature- and humidity-dependent ice nucleation efficiency of ATD particles. Deposition nucleation on ATD particles can be described by a temperature- and relative-humidity-dependent INAS density function ns(T, Sice) with ns(xtherm) = 1.88 ×105 · exp(0.2659 · xtherm) [m-2] , (1) where the temperature- and saturation-dependent function xtherm is defined as xtherm = -(T-273.2)+(Sice-1) ×100, (2) with the saturation ratio with respect to ice Sice >1 and within a temperature range between 226 and 250 K. For lower temperatures, xtherm deviates from a linear behavior with temperature and relative humidity over ice. Also, two different approaches for describing the time dependence of deposition nucleation initiated by ATD particles are proposed. Box model estimates suggest that the time-dependent contribution is only relevant for small cooling rates and low number fractions of ice-active particles.

  1. Breaking Off of Large Ice Masses From Hanging Glaciers

    NASA Astrophysics Data System (ADS)

    Pralong, A.; Funk, M.

    In order to reduce damage to settlements or other installations (roads, railway, etc) and avoid loss of life, a forecast of the final failure time of ice masses is required. At present, the most promising approach for such a prediction is based on the regularity by which certain large ice masses accelerate prior to the instant of collapse. The lim- itation of this forecast lies in short-term irregularities and in the difficulties to obtain sufficiently accurate data. A better physical understanding of the breaking off process is required, in order to improve the forecasting method. Previous analyze has shown that a stepwise crack extension coupling with a viscous flow leads to the observed acceleration function. We propose another approach by considering a local damage evolution law (gener- alized Kachanow's law) coupled with Glen's flow law to simulate the spatial evolu- tion of damage in polycristalline ice, using a finite element computational model. The present study focuses on the transition from a diffuse to a localised damage reparti- tion occurring during the damage evolution. The influence of inhomogeneous initial conditions (inhomogeneity of the mechanical properties of ice, damage inhomogene- ity) and inhomogeneous boundary conditions on the damage repartition are especially investigated.

  2. Mass budget of the glaciers and ice caps of the Queen Elizabeth Islands, Canada, from 1991 to 2015

    NASA Astrophysics Data System (ADS)

    Millan, Romain; Mouginot, Jeremie; Rignot, Eric

    2017-02-01

    Recent studies indicate that the glaciers and ice caps in Queen Elizabeth Islands (QEI), Canada have experienced an increase in ice mass loss during the last two decades, but the contribution of ice dynamics to this loss is not well known. We present a comprehensive mapping of ice velocity using a suite of satellite data from year 1991 to 2015, combined with ice thickness data from NASA Operation IceBridge, to calculate ice discharge. We find that ice discharge increased significantly after 2011 in Prince of Wales Icefield, maintained or decreased in other sectors, whereas glacier surges have little impact on long-term trends in ice discharge. During 1991-2005, the QEI mass loss averaged 6.3 ± 1.1 Gt yr-1, 52% from ice discharge and the rest from surface mass balance (SMB). During 2005-2014, the mass loss from ice discharge averaged 3.5 ± 0.2 Gt yr-1 (10%) versus 29.6 ± 3.0 Gt yr-1 (90%) from SMB. SMB processes therefore dominate the QEI mass balance, with ice dynamics playing a significant role only in a few basins.

  3. A 25-year Record of Antarctic Ice Sheet Elevation and Mass Change

    NASA Astrophysics Data System (ADS)

    Shepherd, A.; Muir, A. S.; Sundal, A.; McMillan, M.; Briggs, K.; Hogg, A.; Engdahl, M.; Gilbert, L.

    2017-12-01

    Since 1992, the European Remote-Sensing (ERS-1 and ERS-2), ENVISAT, and CryoSat-2 satellite radar altimeters have measured the Antarctic ice sheet surface elevation, repeatedly, at approximately monthly intervals. These data constitute the longest continuous record of ice sheet wide change. In this paper, we use these observations to determine changes in the elevation, volume and mass of the East Antarctic and West Antarctic ice sheets, and of parts of the Antarctic Peninsula ice sheet, over a 25-year period. The root mean square difference between elevation rates computed from our survey and 257,296 estimates determined from airborne laser measurements is 54 cm/yr. The longevity of the satellite altimeter data record allows to identify and chart the evolution of changes associated with meteorology and ice flow, and we estimate that 3.6 % of the continental ice sheet, and 21.7 % of West Antarctica, is in a state of dynamical imbalance. Based on this partitioning, we estimate the mass balance of the East and West Antarctic ice sheet drainage basins and the root mean square difference between these and independent estimates derived from satellite gravimetry is less than 5 Gt yr-1.

  4. Anomalously-dense firn in an ice-shelf channel revealed by wide-angle radar

    NASA Astrophysics Data System (ADS)

    Drews, R.; Brown, J.; Matsuoka, K.; Witrant, E.; Philippe, M.; Hubbard, B.; Pattyn, F.

    2015-10-01

    The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g. temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar datasets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. Using a novel algorithm including traveltime inversion and raytracing with a prescribed shape of the depth-density relationship, we show that the depth to internal reflectors, the local ice thickness and depth-averaged densities can reliably be reconstructed. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggests that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals 10 % denser firn inside compared to outside the channel. The denser firn in the ice-shelf channel should be accounted for when using the hydrostatic ice thickness for determining basal melt rates. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.

  5. A new temperature and humidity dependent surface site density approach for deposition ice nucleation

    NASA Astrophysics Data System (ADS)

    Steinke, I.; Hoose, C.; Möhler, O.; Connolly, P.; Leisner, T.

    2014-07-01

    Deposition nucleation experiments with Arizona Test Dust (ATD) as a surrogate for mineral dusts were conducted at the AIDA cloud chamber at temperatures between 220 and 250 K. The influence of the aerosol size distribution and the cooling rate on the ice nucleation efficiencies was investigated. Ice nucleation active surface site (INAS) densities were calculated to quantify the ice nucleation efficiency as a function of temperature, humidity and the aerosol surface area concentration. Additionally, a contact angle parameterization according to classical nucleation theory was fitted to the experimental data in order to relate the ice nucleation efficiencies to contact angle distributions. From this study it can be concluded that the INAS density formulation is a very useful tool to decribe the temperature and humidity dependent ice nucleation efficiency of ATD particles. Deposition nucleation on ATD particles can be described by a temperature and relative humidity dependent INAS density function ns(T, Sice) with ns(xtherm) = 1.88 × 105 \\centerdot exp(0.2659 \\centerdot xtherm) [m-2] (1) where the thermodynamic variable xtherm is defined as xtherm = -(T - 273.2) + (Sice-1) × 100 (2) with Sice>1 and within a temperature range between 226 and 250 K. For lower temperatures, xtherm deviates from a linear behavior with temperature and relative humidity over ice. Two different approaches for describing the time dependence of deposition nucleation initiated by ATD particles are proposed. Box model estimates suggest that the time dependent contribution is only relevant for small cooling rates and low number fractions of ice-active particles.

  6. Balance Mass Flux and Velocity Across the Equilibrium Line in Ice Drainage Systems of Greenland

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Giovinetto, Mario B.; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Estimates of balance mass flux and the depth-averaged ice velocity through the cross-section aligned with the equilibrium line are produced for each of six drainage systems in Greenland. (The equilibrium line, which lies at approximately 1200 m elevation on the ice sheet, is the boundary between the area of net snow accumulation at higher elevations and the areas of net melting at lower elevations around the ice sheet.) Ice drainage divides and six major drainage systems are delineated using surface topography from ERS (European Remote Sensing) radar altimeter data. The net accumulation rate in the accumulation zone bounded by the equilibrium line is 399 Gt/yr and net ablation rate in the remaining area is 231 Gt/yr. (1 GigaTon of ice is 1090 kM(exp 3). The mean balance mass flux and depth-averaged ice velocity at the cross-section aligned with the modeled equilibrium line are 0.1011 Gt kM(exp -2)/yr and 0.111 km/yr, respectively, with little variation in these values from system to system. The ratio of the ice mass above the equilibrium line to the rate of mass output implies an effective exchange time of approximately 6000 years for total mass exchange. The range of exchange times, from a low of 3 ka in the SE drainage system to 14 ka in the NE, suggests a rank as to which regions of the ice sheet may respond more rapidly to climate fluctuations.

  7. Improved estimate of accelerated Antarctica ice mass loses from GRACE, Altimetry and surface mass balance from regional climate model output

    NASA Astrophysics Data System (ADS)

    Velicogna, I.; Sutterley, T. C.; A, G.; van den Broeke, M. R.; Ivins, E. R.

    2016-12-01

    We use Gravity Recovery and Climate Experiment (GRACE) monthly gravity fields to determine the regional acceleration in ice mass loss in Antarctica for 2002-2016. We find that the total mass loss is controlled by only a few regions. In Antarctica, the Amundsen Sea (AS) sector and the Antarctic Peninsula account for 65% and 18%, respectively, of the total loss (186 ± 10 Gt/yr) mainly from ice dynamics. The AS sector contributes most of the acceleration in loss (9 ± 1 Gt/yr2 ), and Queen Maud Land, East Antarctica, is the only sector with a significant mass gain due to a local increase in SMB (57 ± 5 Gt/yr). We compare GRACE regional mass balance estimates with independent estimates from ICESat-1 and Operation IceBridge laser altimetry, CryoSat-2 radar altimetry, and surface mass balance outputs from RACMO2.3. In the Amundsen Sea Embayment of West Antarctica, an area experiencing rapid retreat and mass loss to the sea, we find good agreement between GRACE and altimetry estimates. Comparison of GRACE with these independent techniques in East Antarctic shows that GIA estimates from the new regional ice deglaciation models underestimate the GIA correction in the EAIS interior, which implies larger losses of the Antarctica ice sheet by about 70 Gt/yr. Sectors where we are observing the largest losses are closest to warm circumpolar water, and with polar constriction of the westerlies enhanced by climate warming, we expect these sectors to contribute more and more to sea level as the ice shelves that protect these glaciers will melt faster in contact with more heat from the surrounding oc

  8. Calibrating a surface mass-balance model for Austfonna ice cap, Svalbard

    NASA Astrophysics Data System (ADS)

    Schuler, Thomas Vikhamar; Loe, Even; Taurisano, Andrea; Eiken, Trond; Hagen, Jon Ove; Kohler, Jack

    2007-10-01

    Austfonna (8120 km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (-318 mm w.e.).

  9. Surface Mass Balance of the Greenland Ice Sheet Derived from Paleoclimate Reanalysis

    NASA Astrophysics Data System (ADS)

    Badgeley, J.; Steig, E. J.; Hakim, G. J.; Anderson, J.; Tardif, R.

    2017-12-01

    Modeling past ice-sheet behavior requires independent knowledge of past surface mass balance. Though models provide useful insight into ice-sheet response to climate forcing, if past climate is unknown, then ascertaining the rate and extent of past ice-sheet change is limited to geological and geophysical constraints. We use a novel data-assimilation framework developed under the Last Millennium Reanalysis Project (Hakim et al., 2016) to reconstruct past climate over ice sheets with the intent of creating an independent surface mass balance record for paleo ice-sheet modeling. Paleoclimate data assimilation combines the physics of climate models and the time series evidence of proxy records in an offline, ensemble-based approach. This framework allows for the assimilation of numerous proxy records and archive types while maintaining spatial consistency with known climate dynamics and physics captured by the models. In our reconstruction, we use the Community Climate System Model version 4, CMIP5 last millennium simulation (Taylor et al., 2012; Landrum et al., 2013) and a nearly complete database of ice core oxygen isotope records to reconstruct Holocene surface temperature and precipitation over the Greenland Ice Sheet on a decadal timescale. By applying a seasonality to this reconstruction (from the TraCE-21ka simulation; Liu et al., 2009), our reanalysis can be used in seasonally-based surface mass balance models. Here we discuss the methods behind our reanalysis and the performance of our reconstruction through prediction of unassimilated proxy records and comparison to paleoclimate reconstructions and reanalysis products.

  10. Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard

    NASA Astrophysics Data System (ADS)

    Granskog, Mats A.; Rösel, Anja; Dodd, Paul A.; Divine, Dmitry; Gerland, Sebastian; Martma, Tõnu; Leng, Melanie J.

    2017-03-01

    The salinity and water oxygen isotope composition (δ18O) of 29 first-year (FYI) and second-year (SYI) Arctic sea ice cores (total length 32.0 m) from the drifting ice pack north of Svalbard were examined to quantify the contribution of snow to sea ice mass. Five cores (total length 6.4 m) were analyzed for their structural composition, showing variable contribution of 10-30% by granular ice. In these cores, snow had been entrained in 6-28% of the total ice thickness. We found evidence of snow contribution in about three quarters of the sea ice cores, when surface granular layers had very low δ18O values. Snow contributed 7.5-9.7% to sea ice mass balance on average (including also cores with no snow) based on δ18O mass balance calculations. In SYI cores, snow fraction by mass (12.7-16.3%) was much higher than in FYI cores (3.3-4.4%), while the bulk salinity of FYI (4.9) was distinctively higher than for SYI (2.7). We conclude that oxygen isotopes and salinity profiles can give information on the age of the ice and enables distinction between FYI and SYI (or older) ice in the area north of Svalbard.Plain Language SummaryThe role of snow in sea <span class="hlt">ice</span> <span class="hlt">mass</span> balance is largely two fold. Firstly, it can slow down growth and melt due to its high insulation and high reflectance, but secondly it can actually contribute to sea <span class="hlt">ice</span> growth if the snow cover is turned into <span class="hlt">ice</span>. The latter is largely a consequence of high <span class="hlt">mass</span> of snow on top of sea <span class="hlt">ice</span> that can push the surface of the sea <span class="hlt">ice</span> below sea level and seawater can flood the <span class="hlt">ice</span>. This mixture of seawater and snow can then freeze and add to the growth of sea <span class="hlt">ice</span>. This is very typical in the Antarctic but not believed to be so important in the Arctic. In this work we show, for the first time, that snow actually contributes significantly to the growth of Arctic sea <span class="hlt">ice</span>. This is likely a consequence of the thinning of the Arctic sea <span class="hlt">ice</span>. The conditions in the Arctic, with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.P21B1223L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.P21B1223L"><span>Laboratory measurements of <span class="hlt">ice</span> tensile strength dependence on <span class="hlt">density</span> and concentration of silicate and polymer impurities at low temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Litwin, K. L.; Beyeler, J. D.; Polito, P. J.; Zygielbaum, B. R.; Sklar, L. S.; Collins, G. C.</p> <p>2009-12-01</p> <p>The tensile strength of <span class="hlt">ice</span> bedrock on Titan should strongly influence the effectiveness of the erosional processes responsible for carving the extensive fluvial drainage networks and other surface features visible in images returned by the Cassini and Huygens probes. Recent measurements of the effect of temperature on the tensile strength of low-porosity, polycrystalline <span class="hlt">ice</span>, without impurities, suggest that <span class="hlt">ice</span> bedrock at the Titan surface temperature of 93 K may be as much as five times stronger than <span class="hlt">ice</span> at terrestrial surface temperatures. However, <span class="hlt">ice</span> bedrock on Titan and other outer solar system bodies may have significant porosity, and impurities such silicates or polymers are possible in such <span class="hlt">ices</span>. In this laboratory investigation we are exploring the dependence of tensile strength on the <span class="hlt">density</span> and concentration of impurities, for polycrystalline <span class="hlt">ice</span> across a wide range of temperatures. We use the Brazilian tensile splitting test to measure strength, and control temperature with dry <span class="hlt">ice</span> and liquid nitrogen. The 50 mm diameter <span class="hlt">ice</span> cores are made from a log-normally distributed seed crystal mixture with a median size of 1.4 mm. To control <span class="hlt">ice</span> <span class="hlt">density</span> and porosity we vary the packing <span class="hlt">density</span> of the seed grains in core molds and vary the degree of saturation of the matrix with added near-freezing distilled water. We also vary <span class="hlt">ice</span> <span class="hlt">density</span> by blending in a similarly-sized mixture of angular fragments of two types of impurities, a fine-grained volcanic rock and a polyethylene polymer. Because both types of impurities have greater tensile strength than <span class="hlt">ice</span> at Earth surface temperatures, we expect higher concentrations of impurities to correlate with increased strength for <span class="hlt">ice</span>-rock and <span class="hlt">ice</span>-polymer mixtures. However, at the ultra-cold temperatures of the outer planets, we expect significant divergence in the temperature dependence of <span class="hlt">ice</span> tensile strength for the various mixtures and resulting <span class="hlt">densities</span>. These measurements will help constrain the range of possible</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C44B..01B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C44B..01B"><span>Improving Estimates of Greenland <span class="hlt">Ice</span> Sheet Surface <span class="hlt">Mass</span> Balance with Satellite Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Briggs, K.</p> <p>2016-12-01</p> <p><span class="hlt">Mass</span> losses from the Greenland <span class="hlt">Ice</span> Sheet have been accelerating over recent years (e.g. McMillan et al., 2016; Velicogna et al., 2014). This acceleration has predominantly been linked to increasing rates of negative surface <span class="hlt">mass</span> balance, and in particular, increasing <span class="hlt">ice</span> surface melt rates (e.g. McMillan et al., 2016; Velicogna et al., 2014). At the <span class="hlt">ice</span> sheet scale, SMB is assessed using SMB model outputs, which in addition to enabling understanding of the origin of <span class="hlt">mass</span> balance signals, are required as ancillary data in <span class="hlt">mass</span> balance assessments from altimetry and the <span class="hlt">mass</span> budget method. Due to the importance of SMB for <span class="hlt">mass</span> balance over Greenland and the sensitivity of <span class="hlt">mass</span> balance assessments to SMB model outputs, high accuracy of these models is crucial. A critical limiting factor in SMB modeling is however, a lack of in-situ data that is required for model constraint and evaluation. Such data is limited in time and space due to inherent logistical and financial constraints. Remote sensing datasets, being spatially extensive and relatively densely sampled in both space and time, do not suffer such constraints. Here, we show satellite observations of Greenland SMB. McMillan, M., Leeson, A., Shepherd, A., Briggs, K., Armitage, T. W.K., Hogg, A., Kuipers Munneke, P., van den Broeke, M., Noël, B., van de Berg, W., Ligtenberg, S., Horwath, M., Groh, A. , Muir, A. and Gilbert, L. 2016. A high resolution record of Greenland <span class="hlt">Mass</span> Balance. Geophysical Research Letters. 43, doi:10.1002/2016GL069666 Velicogna, I., Sutterley, T. C. and van den Broeke, M. R. 2014. Regional acceleration in <span class="hlt">ice</span> <span class="hlt">mass</span> loss from Greenland and Antarctica using GRACE time-variable gravity data. Geophysical Research Letters. 41, 8130-8137, doi:10.1002/2014GL061052</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ESS.....310102W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ESS.....310102W"><span>Revised <span class="hlt">Masses</span> and <span class="hlt">Densities</span> of the Planets around Kepler-10</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weiss, Lauren M.; Rogers, Leslie A.; Isaacson, Howard T.; Agol, Eric; Marcy, Geoffrey W.; Rowe, Jason F.; Kipping, David; Fulton, Benjamin; Lissauer, Jack; Howard, Andrew; Clark Fabrycky, Daniel</p> <p>2015-12-01</p> <p>Determining which small exoplanets have stony-iron compositions is necessary for quantifying the occurrence of such planets and for understanding the physics of planet formation. Kepler-10 hosts the stony-iron world Kepler-10b, and also contains what has been reported to be the largest solid silicate-<span class="hlt">ice</span> planet, Kepler-10c. Using 220 radial velocities (RVs), including 72 new precise RVs from Keck-HIRES, and 17 quarters of Kepler photometry, we obtain the most complete picture of the Kepler-10 system to date. We find that Kepler-10b (Rp = 1.47 R⊕) has <span class="hlt">mass</span> 3.70 ± 0.43 M⊕ and <span class="hlt">density</span> 6.44 ± 0.73 g cm-3. Modeling the interior of Kepler-10b as an iron core overlaid with a silicate mantle, we find that the core constitutes 0.17 ± 0.11 of the planet <span class="hlt">mass</span>. For Kepler-10c (Rp = 2.35 R⊕) we measure <span class="hlt">mass</span> 13.32 ± 1.65 M⊕and <span class="hlt">density</span> 5.67 ± 0.70 g cm-3, significantly lower than the <span class="hlt">mass</span> in Dumusque et al. (2014, 17.2±1.9 M⊕). Kepler-10c is not sufficiently dense to have a pure stony-iron composition. Internal compositional modeling reveals that at least 10% of the radius of Kepler-10c is a volatile envelope composed of either hydrogen-helium (0.0027 ± 0.0015 of the <span class="hlt">mass</span>, 0.172±0.037 of the radius) or super-ionic water (0.309±0.11 of the <span class="hlt">mass</span>, 0.305±0.075 of the radius). Transit timing variations (TTVs) of Kepler-10c indicate the likely presence of a third planet in the system, KOI-72.X. The TTVs and RVs are consistent with KOI-72.X having an orbital period of 24, 71, 82, or 101 days, and a <span class="hlt">mass</span> from 1-7 M⊕.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.1259A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.1259A"><span>Greenland <span class="hlt">Ice</span> Sheet seasonal and spatial <span class="hlt">mass</span> variability from model simulations and GRACE (2003-2012)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, Patrick M.; Tedesco, Marco; Schlegel, Nicole-Jeanne; Luthcke, Scott B.; Fettweis, Xavier; Larour, Eric</p> <p>2016-06-01</p> <p>Improving the ability of regional climate models (RCMs) and <span class="hlt">ice</span> sheet models (ISMs) to simulate spatiotemporal variations in the <span class="hlt">mass</span> of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS <span class="hlt">mass</span> loss, studies focusing on <span class="hlt">mass</span> variations at sub-annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for <span class="hlt">mass</span> change are less well understood and modeled, and could potentially play an important role in future GrIS <span class="hlt">mass</span> change. Here, we examine spatiotemporal variations in <span class="hlt">mass</span> over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the January 2003-December 2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated <span class="hlt">mass</span> variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the <span class="hlt">Ice</span> Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS <span class="hlt">mass</span> from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of <span class="hlt">mass</span> inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -178.9 ± 4.4 and -239.4 ± 7.7 Gt yr-1 respectively) in GrIS <span class="hlt">mass</span> over the period examined, but the models appear to underestimate the rate of <span class="hlt">mass</span> loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS <span class="hlt">mass</span> loss is occurring. On an <span class="hlt">ice</span>-sheet-wide scale, the timing of the modeled seasonal cycle of cumulative <span class="hlt">mass</span> (driven by summer <span class="hlt">mass</span> loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-<span class="hlt">ice</span>-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of <span class="hlt">mass</span> change. At these scales, model biases, or processes not accounted for by models related</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....1613359B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....1613359B"><span>Effect of particle surface area on <span class="hlt">ice</span> active site <span class="hlt">densities</span> retrieved from droplet freezing spectra</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beydoun, Hassan; Polen, Michael; Sullivan, Ryan C.</p> <p>2016-10-01</p> <p>Heterogeneous <span class="hlt">ice</span> nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an <span class="hlt">ice</span> active, surface-site-based stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the <span class="hlt">ice</span> nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local <span class="hlt">ice</span> nucleation rates. Upon integration, this yields a full freezing probability function for an <span class="hlt">ice</span> nucleating particle. Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle <span class="hlt">mass</span> or surface area present to derive the commonly used <span class="hlt">ice</span> nuclei active surface (INAS) <span class="hlt">density</span> (ns) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an <span class="hlt">ice</span> nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in <span class="hlt">ice</span> nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations. It is shown that general</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913710C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913710C"><span>Specific findings on <span class="hlt">ice</span> crystal microphysical properties from in-situ observation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter</p> <p>2017-04-01</p> <p>This study focuses on microphysical properties of <span class="hlt">ice</span> particles populating high <span class="hlt">ice</span> water content areas in Mesoscale Convective Systems (MCS). These clouds have been extensively sampled during the High Altitude <span class="hlt">Ice</span> Crystal - High <span class="hlt">Ice</span> Water Content international projects (HAIC-HIWC, Dezitter et al. 2013, Strapp et al. 2015) with the objective of characterizing <span class="hlt">ice</span> particle properties such as size distribution, radar reflectivity and <span class="hlt">ice</span> water content. The in-situ data collected during these campaigns at different temperature levels and in different type of MCS (oceanic, continental) make the HAIC-HIWC data set a unique opportunity to study <span class="hlt">ice</span> particle microphysical properties. Recently, a new approach to retrieve <span class="hlt">ice</span> particle <span class="hlt">mass</span> from in-situ measurements has been developed: a forward model that relates <span class="hlt">ice</span> particles' <span class="hlt">mass</span> to Particle Size Distribution (PSD) and <span class="hlt">Ice</span> Water Content (IWC) is formulated as a linear system of equations and the retrieval process consists in solving the inverse problem with numerical optimization tools (Coutris et al. 2016). In this study, this new method is applied to HAIC-HIWC data set and main outcomes are discussed. First, the method is compared to a classical power-law based method using data from one single flight performed in Darwin area on February, 7th 2014. The observed differences in retrieved quantities such as <span class="hlt">ice</span> particle <span class="hlt">mass</span>, <span class="hlt">ice</span> water content or median <span class="hlt">mass</span> diameter, highlight the potential benefit of abandoning the power law simplistic assumption. The method is then applied to data measured at different cloud temperatures ranging from -40°C to -10°C during several flights of both Darwin 2014 and Cayenne 2015 campaigns. Specific findings about <span class="hlt">ice</span> microphysical properties such as variations of effective <span class="hlt">density</span> with particle size and the influence of cloud temperature on particle effective <span class="hlt">density</span> are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JGRA..110.8103X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JGRA..110.8103X"><span>An <span class="hlt">ice</span>-cream cone model for coronal <span class="hlt">mass</span> ejections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, X. H.; Wang, C. B.; Dou, X. K.</p> <p>2005-08-01</p> <p>In this study, we use an <span class="hlt">ice</span>-cream cone model to analyze the geometrical and kinematical properties of the coronal <span class="hlt">mass</span> ejections (CMEs). Assuming that in the early phase CMEs propagate with near-constant speed and angular width, some useful properties of CMEs, namely the radial speed (v), the angular width (α), and the location at the heliosphere, can be obtained considering the geometrical shapes of a CME as an <span class="hlt">ice</span>-cream cone. This model is improved by (1) using an <span class="hlt">ice</span>-cream cone to show the near real configuration of a CME, (2) determining the radial speed via fitting the projected speeds calculated from the height-time relation in different azimuthal angles, (3) not only applying to halo CMEs but also applying to nonhalo CMEs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V31F..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V31F..04D"><span>Pyroclastic <span class="hlt">density</span> current dynamics and associated hazards at <span class="hlt">ice</span>-covered volcanoes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dufek, J.; Cowlyn, J.; Kennedy, B.; McAdams, J.</p> <p>2015-12-01</p> <p>Understanding the processes by which pyroclastic <span class="hlt">density</span> currents (PDCs) are emplaced is crucial for volcanic hazard prediction and assessment. Snow and <span class="hlt">ice</span> can facilitate PDC generation by lowering the coefficient of friction and by causing secondary hydrovolcanic explosions, promoting remobilisation of proximally deposited material. Where PDCs travel over snow or <span class="hlt">ice</span>, the reduction in surface roughness and addition of steam and meltwater signficantly changes the flow dynamics, affecting PDC velocities and runout distances. Additionally, meltwater generated during transit and after the flow has come to rest presents an immediate secondary lahar hazard that can impact areas many tens of kilometers beyond the intial PDC. This, together with the fact that deposits emplaced on <span class="hlt">ice</span> are rarely preserved means that PDCs over <span class="hlt">ice</span> have been little studied despite the prevalence of summit <span class="hlt">ice</span> at many tall stratovolcanoes. At Ruapehu volcano in the North Island of New Zealand, a monolithologic welded PDC deposit with unusually rounded clasts provides textural evidence for having been transported over glacial <span class="hlt">ice</span>. Here, we present the results of high-resolution multiphase numerical PDC modeling coupled with experimentaly determined rates of water and steam production for the Ruapehu deposits in order to assess the effect of <span class="hlt">ice</span> on the Ruapehu PDC. The results suggest that the presence of <span class="hlt">ice</span> significantly modified the PDC dynamics, with implications for assessing the PDC and associated lahar hazards at Ruapehu and other glaciated volcanoes worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29540750','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29540750"><span>Recent high-resolution Antarctic <span class="hlt">ice</span> velocity maps reveal increased <span class="hlt">mass</span> loss in Wilkes Land, East Antarctica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Qiang; Wang, Hansheng; Shum, C K; Jiang, Liming; Hsu, Hou Tse; Dong, Jinglong</p> <p>2018-03-14</p> <p>We constructed Antarctic <span class="hlt">ice</span> velocity maps from Landsat 8 images for the years 2014 and 2015 at a high spatial resolution (100 m). These maps were assembled from 10,690 scenes of displacement vectors inferred from more than 10,000 optical images acquired from December 2013 through March 2016. We estimated the <span class="hlt">mass</span> discharge of the Antarctic <span class="hlt">ice</span> sheet in 2008, 2014, and 2015 using the Landsat <span class="hlt">ice</span> velocity maps, interferometric synthetic aperture radar (InSAR)-derived <span class="hlt">ice</span> velocity maps (~2008) available from prior studies, and <span class="hlt">ice</span> thickness data. An increased <span class="hlt">mass</span> discharge (53 ± 14 Gt yr -1 ) was found in the East Indian Ocean sector since 2008 due to unexpected widespread glacial acceleration in Wilkes Land, East Antarctica, while the other five oceanic sectors did not exhibit significant changes. However, present-day increased <span class="hlt">mass</span> loss was found by previous studies predominantly in west Antarctica and the Antarctic Peninsula. The newly discovered increased <span class="hlt">mass</span> loss in Wilkes Land suggests that the ocean heat flux may already be influencing <span class="hlt">ice</span> dynamics in the marine-based sector of the East Antarctic <span class="hlt">ice</span> sheet (EAIS). The marine-based sector could be adversely impacted by ongoing warming in the Southern Ocean, and this process may be conducive to destabilization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810633W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810633W"><span><span class="hlt">Ice</span> <span class="hlt">Mass</span> Changes in the Russian High Arctic from Repeat High Resolution Topography.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Willis, Michael; Zheng, Whyjay; Pritchard, Matthew; Melkonian, Andrew; Morin, Paul; Porter, Claire; Howat, Ian; Noh, Myoung-Jong; Jeong, Seongsu</p> <p>2016-04-01</p> <p>We use a combination of ASTER and cartographically derived Digital Elevation Models (DEMs) supplemented with WorldView DEMs, the ArcticDEM and ICESat lidar returns to produce a time-series of <span class="hlt">ice</span> changes occurring in the Russian High Arctic between the mid-20th century and the present. Glaciers on the western, Barents Sea coast of Novaya Zemlya are in a state of general retreat and thinning, while those on the eastern, Kara Sea coast are retreating at a slower rate. Franz Josef Land has a complicated pattern of thinning and thickening, although almost all the thinning is associated with rapid outlet glaciers feeding <span class="hlt">ice</span> shelves. Severnaya Zemlya is also thinning in a complicated manner. A very rapid surging glacier is transferring <span class="hlt">mass</span> into the ocean from the western periphery of the Vavilov <span class="hlt">Ice</span> Cap on October Revolution Island, while glaciers feeding the former Matusevich <span class="hlt">Ice</span> Shelf continue to thin at rates that are faster than those observed during the operational period of ICESat, between 2003 and 2009. Passive microwave studies indicate the total number of melt days is increasing in the Russian Arctic, although much of the melt may refreeze within the firn. It is likely that <span class="hlt">ice</span> dynamic changes will drive <span class="hlt">mass</span> loss for the immediate future. The sub-marine basins beneath several of the <span class="hlt">ice</span> caps in the region suggest the possibility that <span class="hlt">mass</span> loss rates may accelerate in the future.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2773W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2773W"><span>Satellite-derived submarine melt rates and <span class="hlt">mass</span> balance (2011-2015) for Greenland's largest remaining <span class="hlt">ice</span> tongues</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, Nat; Straneo, Fiammetta; Heimbach, Patrick</p> <p>2017-12-01</p> <p><span class="hlt">Ice</span>-shelf-like floating extensions at the termini of Greenland glaciers are undergoing rapid changes with potential implications for the stability of upstream glaciers and the <span class="hlt">ice</span> sheet as a whole. While submarine melting is recognized as a major contributor to <span class="hlt">mass</span> loss, the spatial distribution of submarine melting and its contribution to the total <span class="hlt">mass</span> balance of these floating extensions is incompletely known and understood. Here, we use high-resolution WorldView satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining <span class="hlt">ice</span> tongues - Nioghalvfjerdsbræ (79 North Glacier, 79N), Ryder Glacier (RG), and Petermann Glacier (PG). Submarine melt rates under the <span class="hlt">ice</span> tongues vary considerably, exceeding 50 m a-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the <span class="hlt">ice</span> tongues. We compare the total melt rates to the influx of <span class="hlt">ice</span> to the <span class="hlt">ice</span> tongue to assess their contribution to the current <span class="hlt">mass</span> balance. At Petermann Glacier and Ryder Glacier, we find that the combined submarine and aerial melt approximately balances the <span class="hlt">ice</span> flux from the grounded <span class="hlt">ice</span> sheet. At Nioghalvfjerdsbræ the total melt flux (14.2 ± 0.96 km3 a-1 w.e., water equivalent) exceeds the inflow of <span class="hlt">ice</span> (10.2 ± 0.59 km3 a-1 w.e.), indicating present thinning of the <span class="hlt">ice</span> tongue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........42L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........42L"><span>Surface Energy and <span class="hlt">Mass</span> Balance Model for Greenland <span class="hlt">Ice</span> Sheet and Future Projections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Xiaojian</p> <p></p> <p>The Greenland <span class="hlt">Ice</span> Sheet contains nearly 3 million cubic kilometers of glacial <span class="hlt">ice</span>. If the entire <span class="hlt">ice</span> sheet completely melted, sea level would raise by nearly 7 meters. There is thus considerable interest in monitoring the <span class="hlt">mass</span> balance of the Greenland <span class="hlt">Ice</span> Sheet. Each year, the <span class="hlt">ice</span> sheet gains <span class="hlt">ice</span> from snowfall and loses <span class="hlt">ice</span> through iceberg calving and surface melting. In this thesis, we develop, validate and apply a physics based numerical model to estimate current and future surface <span class="hlt">mass</span> balance of the Greenland <span class="hlt">Ice</span> Sheet. The numerical model consists of a coupled surface energy balance and englacial model that is simple enough that it can be used for long time scale model runs, but unlike previous empirical parameterizations, has a physical basis. The surface energy balance model predicts <span class="hlt">ice</span> sheet surface temperature and melt production. The englacial model predicts the evolution of temperature and meltwater within the <span class="hlt">ice</span> sheet. These two models can be combined with estimates of precipitation (snowfall) to estimate the <span class="hlt">mass</span> balance over the Greenland <span class="hlt">Ice</span> Sheet. We first compare model performance with in-situ observations to demonstrate that the model works well. We next evaluate how predictions are degraded when we statistically downscale global climate data. We find that a simple, nearest neighbor interpolation scheme with a lapse rate correction is able to adequately reproduce melt patterns on the Greenland <span class="hlt">Ice</span> Sheet. These results are comparable to those obtained using empirical Positive Degree Day (PDD) methods. Having validated the model, we next drove the <span class="hlt">ice</span> sheet model using the suite of atmospheric model runs available through the CMIP5 atmospheric model inter-comparison, which in turn built upon the RCP 8.5 (business as usual) scenarios. From this exercise we predict how much surface melt production will increase in the coming century. This results in 4-10 cm sea level equivalent, depending on the CMIP5 models. Finally, we try to bound melt water</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814608M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814608M"><span>Present and Future Surface <span class="hlt">Mass</span> Budget of Small Arctic <span class="hlt">Ice</span> Caps in a High Resolution Regional Climate Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mottram, Ruth; Langen, Peter; Koldtoft, Iben; Midefelt, Linnea; Hesselbjerg Christensen, Jens</p> <p>2016-04-01</p> <p>Globally, small <span class="hlt">ice</span> caps and glaciers make a substantial contribution to sea level rise; this is also true in the Arctic. Around Greenland small <span class="hlt">ice</span> caps are surprisingly important to the total <span class="hlt">mass</span> balance from the island as their marginal coastal position means they receive a large amount of precipitation and also experience high surface melt rates. Since small <span class="hlt">ice</span> caps and glaciers have had a disproportionate number of long-term monitoring and observational schemes in the Arctic, likely due to their relative accessibility, they can also be a valuable source of data. However, in climate models the surface <span class="hlt">mass</span> balance contributions are often not distinguished from the main <span class="hlt">ice</span> sheet and the presence of high relief topography is difficult to capture in coarse resolution climate models. At the same time, the diminutive size of marginal <span class="hlt">ice</span> <span class="hlt">masses</span> in comparison to the <span class="hlt">ice</span> sheet makes modelling their <span class="hlt">ice</span> dynamics difficult. Using observational data from the Devon <span class="hlt">Ice</span> Cap in Arctic Canada and the Renland <span class="hlt">Ice</span> Cap in Eastern Greenland, we assess the success of a very high resolution (~5km) regional climate model, HIRHAM5 in capturing the surface <span class="hlt">mass</span> balance (SMB) of these small <span class="hlt">ice</span> caps. The model is forced with ERA-Interim and we compare observed mean SMB and the interannual variability to assess model performance. The steep gradient in topography around Renland is challenging for climate models and additional statistical corrections are required to fit the calculated surface <span class="hlt">mass</span> balance to the high relief topography. Results from a modelling experiment at Renland <span class="hlt">Ice</span> Cap shows that this technique produces a better fit between modelled and observed surface topography. We apply this statistical relationship to modelled SMB on the Devon <span class="hlt">Ice</span> Cap and use the long time series of observations from this glacier to evaluate the model and the smoothed SMB. Measured SMB values from a number of other small <span class="hlt">ice</span> caps including Mittivakkat and A.P. Olsen <span class="hlt">ice</span> cap are also compared</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C14B..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C14B..04B"><span>Understanding <span class="hlt">Ice</span> Shelf Basal Melting Using Convergent ICEPOD Data Sets: ROSETTA-<span class="hlt">Ice</span> Study of Ross <span class="hlt">Ice</span> Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bell, R. E.; Frearson, N.; Tinto, K. J.; Das, I.; Fricker, H. A.; Siddoway, C. S.; Padman, L.</p> <p>2017-12-01</p> <p> magnetic anomalies, and deep bathymetry. The West Antarctic side displays high amplitude magnetic anomalies, lower <span class="hlt">densities</span> and shallower water depths. The geologically-controlled bathymetry influences the access of water <span class="hlt">masses</span> capable of basal melting into the <span class="hlt">ice</span> shelf cavity with the deep troughs on the East Antarctic side facilitating melting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRF..119.1995M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRF..119.1995M"><span>Field-calibrated model of melt, refreezing, and runoff for polar <span class="hlt">ice</span> caps: Application to Devon <span class="hlt">Ice</span> Cap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, Richard M.; Mair, Douglas W. F.; Nienow, Peter W.; Bell, Christina; Burgess, David O.; Wright, Andrew P.</p> <p>2014-09-01</p> <p>Understanding the controls on the amount of surface meltwater that refreezes, rather than becoming runoff, over polar <span class="hlt">ice</span> <span class="hlt">masses</span> is necessary for modeling their surface <span class="hlt">mass</span> balance and ultimately for predicting their future contributions to global sea level change. We present a modified version of a physically based model that includes an energy balance routine and explicit calculation of near-surface meltwater refreezing capacity, to simulate the evolution of near-surface <span class="hlt">density</span> and temperature profiles across Devon <span class="hlt">Ice</span> Cap in Arctic Canada. Uniquely, our model is initiated and calibrated using high spatial resolution measurements of snow and firn <span class="hlt">densities</span> across almost the entire elevation range of the <span class="hlt">ice</span> cap for the summer of 2004 and subsequently validated with the same type of measurements obtained during the very different meteorological conditions of summer 2006. The model captures the spatial variability across the transect in bulk snowpack properties although it slightly underestimates the flow of meltwater into the firn of previous years. The percentage of meltwater that becomes runoff is similar in both years; however, the spatial pattern of this melt-runoff relationship is different in the 2 years. The model is found to be insensitive to variation in the depth of impermeable layers within the firn but is very sensitive to variation in air temperature, since the refreezing capacity of firn decreases with increasing temperature. We highlight that the sensitivity of the <span class="hlt">ice</span> cap's surface <span class="hlt">mass</span> balance to air temperature is itself dependent on air temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C21B0585S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C21B0585S"><span><span class="hlt">Mass</span> Balance of the Northern Antarctic Peninsula and its Ongoing Response to <span class="hlt">Ice</span> Shelf Loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scambos, T. A.; Berthier, E.; Haran, T. M.; Shuman, C. A.; Cook, A. J.; Bohlander, J. A.</p> <p>2012-12-01</p> <p>An assessment of the most rapidly changing areas of the Antarctic Peninsula (north of 66°S) shows that <span class="hlt">ice</span> <span class="hlt">mass</span> loss for the region is dominated by areas affected by eastern-Peninsula <span class="hlt">ice</span> shelf losses in the past 20 years. Little if any of the <span class="hlt">mass</span> loss is compensated by increased snowfall in the northwestern or far northern areas. We combined satellite stereo-image DEM differencing and ICESat-derived along-track elevation changes to measure <span class="hlt">ice</span> <span class="hlt">mass</span> loss for the Antarctic Peninsula north of 66°S between 2001-2010, focusing on the ICESat-1 period of operation (2003-2009). This mapping includes all <span class="hlt">ice</span> drainages affected by recent <span class="hlt">ice</span> shelf loss in the northeastern Peninsula (Prince Gustav, Larsen Inlet, Larsen A, and Larsen B) as well as James Ross Island, Vega Island, Anvers Island, Brabant Island and the adjacent west-flowing glaciers. Polaris Glacier (feeding the Larsen Inlet, which collapsed in 1986) is an exception, and may have stabilized. Our method uses ASTER and SPOT-5 stereo-image DEMs to determine dh/dt for elevations below 800 m; at higher elevations ICESat along-track elevation differencing is used. To adjust along-track path offsets between its 2003-2009 campaigns, we use a recent DEM of the Peninsula to establish and correct for cross-track slope (Cook et al., 2012, doi:10.5194/essdd-5-365-2012; http://nsidc.org/data/nsidc-0516.html) . We reduce the effect of possible seasonal variations in elevation by using only integer-year repeats of the ICESat tracks for comparison. <span class="hlt">Mass</span> losses are dominated by the major glaciers that had flowed into the Prince Gustav (Boydell, Sjorgren, Röhss), Larsen A (Edgeworth, Bombardier, Dinsmoor, Drygalski), and Larsen B (Hektoria, Jorum, and Crane) embayments. The pattern of <span class="hlt">mass</span> loss emphasizes the significant and multi-decadal response to <span class="hlt">ice</span> shelf loss. Areas with shelf losses occurring 30 to 100s of years ago seem to be relatively stable or losing <span class="hlt">mass</span> only slowly (western glaciers, northernmost areas). The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120014297','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120014297"><span>An Iterated Global Mascon Solution with Focus on Land <span class="hlt">Ice</span> <span class="hlt">Mass</span> Evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Luthcke, S. B.; Sabaka, T.; Rowlands, D. D.; Lemoine, F. G.; Loomis, B. D.; Boy, J. P.</p> <p>2012-01-01</p> <p>Land <span class="hlt">ice</span> <span class="hlt">mass</span> evolution is determined from a new GRACE global mascon solution. The solution is estimated directly from the reduction of the inter-satellite K-band range rate observations taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons are estimated with 10-day and 1-arc-degree equal area sampling, applying anisotropic constraints for enhanced temporal and spatial resolution of the recovered land <span class="hlt">ice</span> signal. The details of the solution are presented including error and resolution analysis. An Ensemble Empirical Mode Decomposition (EEMD) adaptive filter is applied to the mascon solution time series to compute timing of balance seasons and annual <span class="hlt">mass</span> balances. The details and causes of the spatial and temporal variability of the land <span class="hlt">ice</span> regions studied are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JChPh.147d4501G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JChPh.147d4501G"><span>Influence of sample preparation on the transformation of low-<span class="hlt">density</span> to high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span>: An explanation based on the potential energy landscape</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giovambattista, Nicolas; Starr, Francis W.; Poole, Peter H.</p> <p>2017-07-01</p> <p>Experiments and computer simulations of the transformations of amorphous <span class="hlt">ices</span> display different behaviors depending on sample preparation methods and on the rates of change of temperature and pressure to which samples are subjected. In addition to these factors, simulation results also depend strongly on the chosen water model. Using computer simulations of the ST2 water model, we study how the sharpness of the compression-induced transition from low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (LDA) to high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA) is influenced by the preparation of LDA. By studying LDA samples prepared using widely different procedures, we find that the sharpness of the LDA-to-HDA transformation is correlated with the depth of the initial LDA sample in the potential energy landscape (PEL), as characterized by the inherent structure energy. Our results show that the complex phenomenology of the amorphous <span class="hlt">ices</span> reported in experiments and computer simulations can be understood and predicted in a unified way from knowledge of the PEL of the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29016475','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29016475"><span>Relationship between Physiological Off-<span class="hlt">Ice</span> Testing, On-<span class="hlt">Ice</span> Skating, and Game Performance in Division I Women's <span class="hlt">Ice</span> Hockey Players.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boland, Michelle; Miele, Emily M; Delude, Katie</p> <p>2017-10-07</p> <p>The purpose was to identify off-<span class="hlt">ice</span> testing variables that correlate to skating and game performance in Division I collegiate women <span class="hlt">ice</span> hockey players. Twenty female, forward and defensive players (19.95 ± 1.35 yr) were assessed for weight, height, percent fat <span class="hlt">mass</span> (%FAT), bone mineral <span class="hlt">density</span>, predicted one repetition maximum (RM) absolute and relative (REL%) bench press (BP) and hex bar deadlift (HDL), lower body explosive power, anaerobic power, countermovement vertical jump (CMJ), maximum inspiratory pressure (MIP), and on-<span class="hlt">ice</span> repeated skate sprint (RSS) performance. The on-<span class="hlt">ice</span> RSS test included 6 timed 85.6 m sprints with participants wearing full hockey equipment; fastest time (FT), average time (AT) and fatigue index (FI) for the first length skate (FLS; 10 m) and total length skate (TLS; 85.6 m) were used for analysis. Game performance was evaluated with game statistics: goals, assists, points, plus-minus, and shots on goal (SOG). Correlation coefficients were used to determine relationships. Percent fat <span class="hlt">mass</span> was positively correlated (p < 0.05) with FLS-FI and TLS-AT; TLS-FT was negatively correlated with REL%HDL; BP-RM was negatively correlated with FLS-FT and FLS-AT; MIP positively correlated with assists, points, and SOG; FLS-AT negatively correlated with assists. Game performance in women <span class="hlt">ice</span> hockey players may be enhanced by greater MIP, repeat acceleration ability, and mode-specific training. Faster skating times were associated with lower %FAT. Skating performance in women <span class="hlt">ice</span> hockey players may be enhanced by improving body composition, anaerobic power, and both lower and upper body strength in off-<span class="hlt">ice</span> training.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002071','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002071"><span>Analysis of Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">Mass</span> Balance from ICESat Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui</p> <p>2011-01-01</p> <p>If protoplanets formed from 10 to 20 kilometer diameter planetesimals in a runaway accretion process prior to their oligarchic growth into the terrestrial planets, it is only logical to ask where these planetesimals may have formed in order to assess the initial composition of the Earth. We have used Weidenschilling's model for the formation of comets (1997) to calculate an efficiency factor for the formation of planetesimals from the solar nebula, then used this factor to calculate the feeding zones that contribute to material contained within 10, 15 and 20 kilometer diameter planetesimals at 1 A.V. as a function of nebular <span class="hlt">mass</span>. We find that for all reasonable nebular <span class="hlt">masses</span>, these planetesimals contain a minimum of 3% water as <span class="hlt">ice</span> by <span class="hlt">mass</span>. The fraction of <span class="hlt">ice</span> increases as the planetesimals increase in size and as the nebular <span class="hlt">mass</span> decreases, since both factors increase the feeding zones from which solids in the final planetesimals are drawn. Is there really a problem with the current accretion scenario that makes the Earth too dry, or is it possible that the nascent Earth lost significant quantities of water in the final stages of accretion?</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.1553S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.1553S"><span>Sea-<span class="hlt">ice</span> deformation in a coupled ocean-sea-<span class="hlt">ice</span> model and in satellite remote sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spreen, Gunnar; Kwok, Ron; Menemenlis, Dimitris; Nguyen, An T.</p> <p>2017-07-01</p> <p>A realistic representation of sea-<span class="hlt">ice</span> deformation in models is important for accurate simulation of the sea-<span class="hlt">ice</span> <span class="hlt">mass</span> balance. Simulated sea-<span class="hlt">ice</span> deformation from numerical simulations with 4.5, 9, and 18 km horizontal grid spacing and a viscous-plastic (VP) sea-<span class="hlt">ice</span> rheology are compared with synthetic aperture radar (SAR) satellite observations (RGPS, RADARSAT Geophysical Processor System) for the time period 1996-2008. All three simulations can reproduce the large-scale <span class="hlt">ice</span> deformation patterns, but small-scale sea-<span class="hlt">ice</span> deformations and linear kinematic features (LKFs) are not adequately reproduced. The mean sea-<span class="hlt">ice</span> total deformation rate is about 40 % lower in all model solutions than in the satellite observations, especially in the seasonal sea-<span class="hlt">ice</span> zone. A decrease in model grid spacing, however, produces a higher <span class="hlt">density</span> and more localized <span class="hlt">ice</span> deformation features. The 4.5 km simulation produces some linear kinematic features, but not with the right frequency. The dependence on length scale and probability <span class="hlt">density</span> functions (PDFs) of absolute divergence and shear for all three model solutions show a power-law scaling behavior similar to RGPS observations, contrary to what was found in some previous studies. Overall, the 4.5 km simulation produces the most realistic divergence, vorticity, and shear when compared with RGPS data. This study provides an evaluation of high and coarse-resolution viscous-plastic sea-<span class="hlt">ice</span> simulations based on spatial distribution, time series, and power-law scaling metrics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H11C1073Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H11C1073Z"><span>A New Approach to Modeling <span class="hlt">Densities</span> and Equilibria of <span class="hlt">Ice</span> and Gas Hydrate Phases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zyvoloski, G.; Lucia, A.; Lewis, K. C.</p> <p>2011-12-01</p> <p>The Gibbs-Helmholtz Constrained (GHC) equation is a new cubic equation of state that was recently derived by Lucia (2010) and Lucia et al. (2011) by constraining the energy parameter in the Soave form of the Redlich-Kwong equation to satisfy the Gibbs-Helmholtz equation. The key attributes of the GHC equation are: 1) It is a multi-scale equation because it uses the internal energy of departure, UD, as a natural bridge between the molecular and bulk phase length scales. 2) It does not require acentric factors, volume translation, regression of parameters to experimental data, binary (kij) interaction parameters, or other forms of empirical correlations. 3) It is a predictive equation of state because it uses a database of values of UD determined from NTP Monte Carlo simulations. 4) It can readily account for differences in molecular size and shape. 5) It has been successfully applied to non-electrolyte mixtures as well as weak and strong aqueous electrolyte mixtures over wide ranges of temperature, pressure and composition to predict liquid <span class="hlt">density</span> and phase equilibrium with up to four phases. 6) It has been extensively validated with experimental data. 7) The AAD% error between predicted and experimental liquid <span class="hlt">density</span> is 1% while the AAD% error in phase equilibrium predictions is 2.5%. 8) It has been used successfully within the subsurface flow simulation program FEHM. In this work we describe recent extensions of the multi-scale predictive GHC equation to modeling the phase <span class="hlt">densities</span> and equilibrium behavior of hexagonal <span class="hlt">ice</span> and gas hydrates. In particular, we show that radial distribution functions, which can be determined by NTP Monte Carlo simulations, can be used to establish correct standard state fugacities of 1h <span class="hlt">ice</span> and gas hydrates. From this, it is straightforward to determine both the phase <span class="hlt">density</span> of <span class="hlt">ice</span> or gas hydrates as well as any equilibrium involving <span class="hlt">ice</span> and/or hydrate phases. A number of numerical results for mixtures of N2, O2, CH4, CO2, water</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25345526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25345526"><span>Immersion freezing of supermicron mineral dust particles: freezing results, testing different schemes for describing <span class="hlt">ice</span> nucleation, and <span class="hlt">ice</span> nucleation active site <span class="hlt">densities</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wheeler, M J; Mason, R H; Steunenberg, K; Wagstaff, M; Chou, C; Bertram, A K</p> <p>2015-05-14</p> <p><span class="hlt">Ice</span> nucleation on mineral dust particles is known to be an important process in the atmosphere. To accurately implement <span class="hlt">ice</span> nucleation on mineral dust particles in atmospheric simulations, a suitable theory or scheme is desirable to describe laboratory freezing data in atmospheric models. In the following, we investigated <span class="hlt">ice</span> nucleation by supermicron mineral dust particles [kaolinite and Arizona Test Dust (ATD)] in the immersion mode. The median freezing temperature for ATD was measured to be approximately -30 °C compared with approximately -36 °C for kaolinite. The freezing results were then used to test four different schemes previously used to describe <span class="hlt">ice</span> nucleation in atmospheric models. In terms of ability to fit the data (quantified by calculating the reduced chi-squared values), the following order was found for ATD (from best to worst): active site, pdf-α, deterministic, single-α. For kaolinite, the following order was found (from best to worst): active site, deterministic, pdf-α, single-α. The variation in the predicted median freezing temperature per decade change in the cooling rate for each of the schemes was also compared with experimental results from other studies. The deterministic model predicts the median freezing temperature to be independent of cooling rate, while experimental results show a weak dependence on cooling rate. The single-α, pdf-α, and active site schemes all agree with the experimental results within roughly a factor of 2. On the basis of our results and previous results where different schemes were tested, the active site scheme is recommended for describing the freezing of ATD and kaolinite particles. We also used our <span class="hlt">ice</span> nucleation results to determine the <span class="hlt">ice</span> nucleation active site (INAS) <span class="hlt">density</span> for the supermicron dust particles tested. Using the data, we show that the INAS <span class="hlt">densities</span> of supermicron kaolinite and ATD particles studied here are smaller than the INAS <span class="hlt">densities</span> of submicron kaolinite and ATD particles</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27984880','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27984880"><span>Potential energy landscape of the apparent first-order phase transition between low-<span class="hlt">density</span> and high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Giovambattista, Nicolas; Sciortino, Francesco; Starr, Francis W; Poole, Peter H</p> <p>2016-12-14</p> <p>The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics to describe supercooled liquids and glasses. Here we use the PEL formalism and computer simulations to study the pressure-induced transformations between low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (LDA) and high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA) at different temperatures. We employ the ST2 water model for which the LDA-HDA transformations are remarkably sharp, similar to what is observed in experiments, and reminiscent of a first-order phase transition. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that low-<span class="hlt">density</span> liquid (LDL) configurations are located in the same megabasin as LDA, and that high-<span class="hlt">density</span> liquid (HDL) configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid is different from the path followed by the amorphous solid. At higher pressure, we also study the liquid-to-<span class="hlt">ice</span>-VII first-order phase transition, and find that the behavior of the PEL properties across this transition is qualitatively similar to the changes found during the LDA-HDA transformation. This similarity supports the interpretation that the LDA-HDA transformation is a first-order phase transition between out-of-equilibrium states. Finally, we compare the PEL properties explored during the LDA-HDA transformations in ST2 water with those reported previously for SPC/E water, for which the LDA-HDA transformations are rather smooth. This comparison illuminates the previous work showing that, at accessible computer times scales, a liquid-liquid phase transition occurs in the case of ST2 water, but not for SPC/E water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JChPh.145v4501G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JChPh.145v4501G"><span>Potential energy landscape of the apparent first-order phase transition between low-<span class="hlt">density</span> and high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giovambattista, Nicolas; Sciortino, Francesco; Starr, Francis W.; Poole, Peter H.</p> <p>2016-12-01</p> <p>The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics to describe supercooled liquids and glasses. Here we use the PEL formalism and computer simulations to study the pressure-induced transformations between low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (LDA) and high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA) at different temperatures. We employ the ST2 water model for which the LDA-HDA transformations are remarkably sharp, similar to what is observed in experiments, and reminiscent of a first-order phase transition. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that low-<span class="hlt">density</span> liquid (LDL) configurations are located in the same megabasin as LDA, and that high-<span class="hlt">density</span> liquid (HDL) configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid is different from the path followed by the amorphous solid. At higher pressure, we also study the liquid-to-<span class="hlt">ice</span>-VII first-order phase transition, and find that the behavior of the PEL properties across this transition is qualitatively similar to the changes found during the LDA-HDA transformation. This similarity supports the interpretation that the LDA-HDA transformation is a first-order phase transition between out-of-equilibrium states. Finally, we compare the PEL properties explored during the LDA-HDA transformations in ST2 water with those reported previously for SPC/E water, for which the LDA-HDA transformations are rather smooth. This comparison illuminates the previous work showing that, at accessible computer times scales, a liquid-liquid phase transition occurs in the case of ST2 water, but not for SPC/E water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC43J..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC43J..06R"><span>The direct mechanical influence of sea <span class="hlt">ice</span> state on <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss via iceberg mélange</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robel, A.</p> <p>2017-12-01</p> <p>The interaction between sea <span class="hlt">ice</span> and land <span class="hlt">ice</span> has typically been considered as a large-scale exchange of moisture, heat and salinity through the ocean and atmosphere. However, recent observations from marine-terminating glaciers in Greenland indicate that the long-term decline of local sea <span class="hlt">ice</span> cover has been accompanied by an increase in nearby iceberg calving and associated <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss. Near glacier calving fronts, sea <span class="hlt">ice</span> binds icebergs together into an aggregate granular material known as iceberg mélange. Studies have hypothesized that mélange may suppress calving by exerting a mechanical buttressing force directly on the glacier terminus. Here, we show explicitly how sea <span class="hlt">ice</span> thickness and concentration play a critical role in setting the material strength of mélange. To do so, we adapt a discrete element model to simulate mélange as a cohesive granular material. In these simulations, mélange laden with thick, dense, landfast sea <span class="hlt">ice</span> can produce enough resistance to shut down calving at the terminus. When sea <span class="hlt">ice</span> thins, mélange weakens, reducing the mechanical force of mélange on the glacier terminus, and increasing the likelihood of calving. We discuss whether longer periods of sea-<span class="hlt">ice</span>-free conditions in winter may lead to a transition from currently slow calving, predominantly occurring in the summer, to rapid calving, occurring throughout the year. We also discuss the potential role of freshwater discharge in promoting sea <span class="hlt">ice</span> formation in fjords, potentially strengthening mélange.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007E%26PSL.264..391S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007E%26PSL.264..391S"><span>Regional <span class="hlt">ice-mass</span> changes and glacial-isostatic adjustment in Antarctica from GRACE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sasgen, Ingo; Martinec, Zdeněk; Fleming, Kevin</p> <p>2007-12-01</p> <p>We infer regional <span class="hlt">mass</span> changes in Antarctica using ca. 4 years of Gravity Recovery and Climate Experiment (GRACE) level 2 data. We decompose the time series of the Stokes coefficients into their linear as well as annual and semi-annual components by a least-squares adjustment and apply a statistical reliability test to the Stokes potential-coefficients' linear temporal trends. <span class="hlt">Mass</span> changes in three regions of Antarctica that display prominent geoid-height change are determined by adjusting predictions of glacier melting at the tip of the Antarctic Peninsula and in the Amundsen Sea Sector, and of the glacial-isostatic adjustment (GIA) over the Ronne <span class="hlt">Ice</span> Shelf. We use the GFZ RL04, CNES RL01C, JPL RL04 and CSR RL04 potential-coefficient releases, and show that, although all data sets consistently reflect the prominent <span class="hlt">mass</span> changes, differences in the <span class="hlt">mass</span>-change estimates are considerably larger than the uncertainties estimated by the propagation of the GRACE errors. We then use the bootstrapping method based on the four releases and six time intervals, each with 3.5 years of data, to quantify the variability of the mean <span class="hlt">mass</span>-change estimates. We find 95% of our estimates to lie within 0.08 and 0.09 mm/a equivalent sea-level (ESL) change for the Antarctic Peninsula and within 0.18 and 0.20 mm/a ESL for the Amundsen Sea Sector. Forward modelling of the GIA over the Ronne <span class="hlt">Ice</span> Shelf region suggests that the Antarctic continent was covered by 8.4 to 9.4 m ESL of additional <span class="hlt">ice</span> during the Last-Glacial Maximum (ca. 22 to 15 ka BP). With regards to the mantle-viscosity values and the glacial history used, this value is considered as a minimum estimate. The <span class="hlt">mass</span>-change estimates derived from all GRACE releases and time intervals lie within ca. 20% (Amundsen Sea Sector), 30% (Antarctic Peninsula) and 50% (Ronne <span class="hlt">Ice</span> Shelf region) of the bootstrap-estimated mean, demonstrating the reliability of results obtained using GRACE observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4810625N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4810625N"><span>Determination of CME 3D parameters based on a new full <span class="hlt">ice</span>-cream cone model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Na, Hyeonock; Moon, Yong-Jae</p> <p>2017-08-01</p> <p>In space weather forecast, it is important to determine three-dimensional properties of CMEs. Using 29 limb CMEs, we examine which cone type is close to a CME three-dimensional structure. We find that most CMEs have near full <span class="hlt">ice</span>-cream cone structure which is a symmetrical circular cone combined with a hemisphere. We develop a full <span class="hlt">ice</span>-cream cone model based on a new methodology that the full <span class="hlt">ice</span>-cream cone consists of many flat cones with different heights and angular widths. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model). In addition, we derive CME mean <span class="hlt">density</span> (ρmean=Mtotal/Vcone) based on the full <span class="hlt">ice</span>-cream cone structure. For several limb events, we determine CME <span class="hlt">mass</span> by applying the Solarsoft procedure (e.g., cme_<span class="hlt">mass</span>.pro) to SOHO/LASCO C3 images. CME volumes are estimated from the full <span class="hlt">ice</span>-cream cone structure. From the power-law relationship between CME mean <span class="hlt">density</span> and its height, we estimate CME mean <span class="hlt">densities</span> at 20 solar radii (Rs). We will compare the CME <span class="hlt">densities</span> at 20 Rs with their corresponding ICME <span class="hlt">densities</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28362423','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28362423"><span><span class="hlt">Ice</span> Generation and the Heat and <span class="hlt">Mass</span> Transfer Phenomena of Introducing Water to a Cold Bath of Brine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yun, Xiao; Quarini, Giuseppe L</p> <p>2017-03-13</p> <p>We demonstrate a method for the study of the heat and <span class="hlt">mass</span> transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed that, under the proper conditions, <span class="hlt">ice</span> can be produced when water is introduced to a bath of cold brine. To make <span class="hlt">ice</span> form, in addition to having the brine and water mix, the rate of heat transfer must bypass that of <span class="hlt">mass</span> transfer. When water is introduced in the form of tiny droplets to the brine surface, the mode of heat and <span class="hlt">mass</span> transfer is by diffusion. The buoyancy stops water from mixing with the brine underneath, but as the <span class="hlt">ice</span> grows thicker, it slows down the rate of heat transfer, making <span class="hlt">ice</span> more difficult to grow as a result. When water is introduced inside the brine in the form of a flow, a number of factors are found to influence how much <span class="hlt">ice</span> can form. Brine temperature and concentration, which are the driving forces of heat and <span class="hlt">mass</span> transfer, respectively, can affect the water-to-<span class="hlt">ice</span> conversion ratio; lower bath temperatures and brine concentrations encourage more <span class="hlt">ice</span> to form. The flow rheology, which can directly affect both the heat and <span class="hlt">mass</span> transfer coefficients, is also a key factor. In addition, the flow rheology changes the area of contact of the flow with the bulk fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13C0833S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13C0833S"><span>Using ATM laser altimetry to constrain surface <span class="hlt">mass</span> balance estimates and supraglacial hydrology of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Studinger, M.; Medley, B.; Manizade, S.; Linkswiler, M. A.</p> <p>2016-12-01</p> <p>Repeat airborne laser altimetry measurements can provide large-scale field observations to better quantify spatial and temporal variability of surface processes contributing to seasonal elevation change and therefore surface <span class="hlt">mass</span> balance. As part of NASA's Operation <span class="hlt">Ice</span>Bridge the Airborne Topographic Mapper (ATM) laser altimeter measured the surface elevation of the Greenland <span class="hlt">Ice</span> Sheet during spring (March - May) and fall (September - October) of 2015. Comparison of the two surveys reveals a general trend of thinning for outlet glaciers and for the <span class="hlt">ice</span> sheet in a manner related to elevation and latitude. In contrast, some thickening is observed on the west (but not on the east) side of the <span class="hlt">ice</span> divide above 2200 m elevation in the southern half, below latitude 69°N.The observed magnitude and spatial patterns of the summer melt signal can be utilized as input into <span class="hlt">ice</span> sheet models and for validating reanalysis of regional climate models such as RACMO and MAR. We use seasonal anomalies in MERRA-2 climate fields (temperature, precipitation) to understand the observed spatial signal in seasonal change. Aside from surface elevation change, runoff from meltwater pooling in supraglacial lakes and meltwater channels accounts for at least half of the total <span class="hlt">mass</span> loss. The ability of the ATM laser altimeters to image glacial hydrological features in 3-D and determine the depth of supraglacial lakes could be used for process studies and for quantifying melt processes over large scales. The 1-meter footprint diameter of ATM laser on the surface, together with a high shot <span class="hlt">density</span>, allows for the production of large-scale, high-resolution, geodetic quality DEMs (50 x 50 cm) suitable for fine-scale glacial hydrology research and as input to hydrological models quantifying runoff.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PNAS..114.8193P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PNAS..114.8193P"><span>Diffusive dynamics during the high-to-low <span class="hlt">density</span> transition in amorphous <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perakis, Fivos; Amann-Winkel, Katrin; Lehmkühler, Felix; Sprung, Michael; Mariedahl, Daniel; Sellberg, Jonas A.; Pathak, Harshad; Späh, Alexander; Cavalca, Filippo; Schlesinger, Daniel; Ricci, Alessandro; Jain, Avni; Massani, Bernhard; Aubree, Flora; Benmore, Chris J.; Loerting, Thomas; Grübel, Gerhard; Pettersson, Lars G. M.; Nilsson, Anders</p> <p>2017-08-01</p> <p>Water exists in high- and low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-<span class="hlt">density</span> liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-<span class="hlt">density</span> transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-<span class="hlt">density</span> transition in amorphous <span class="hlt">ice</span> at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-<span class="hlt">density</span> form at 130 K, but remains diffusive. The diffusive character of both the high- and low-<span class="hlt">density</span> forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid-liquid transition in the ultraviscous regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GGG....18.2099C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GGG....18.2099C"><span>Short-term variations of Icelandic <span class="hlt">ice</span> cap <span class="hlt">mass</span> inferred from cGPS coordinate time series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio</p> <p>2017-06-01</p> <p>As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term <span class="hlt">ice</span> cap <span class="hlt">mass</span> changes. We calculate unit responses to each of the five largest <span class="hlt">ice</span> caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate <span class="hlt">ice</span> <span class="hlt">mass</span> variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter <span class="hlt">mass</span> balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1σ confidence bounds of the inversion. We identify nonperiodic <span class="hlt">ice</span> <span class="hlt">mass</span> changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced <span class="hlt">ice</span> surface albedo or decreased melting due to <span class="hlt">ice</span> cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5426515','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5426515"><span>Sea-level feedback lowers projections of future Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">mass</span> loss</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gomez, Natalya; Pollard, David; Holland, David</p> <p>2015-01-01</p> <p>The stability of marine sectors of the Antarctic <span class="hlt">Ice</span> Sheet (AIS) in a warming climate has been identified as the largest source of uncertainty in projections of future sea-level rise. Sea-level fall near the grounding line of a retreating marine <span class="hlt">ice</span> sheet has a stabilizing influence on the <span class="hlt">ice</span> sheets, and previous studies have established the importance of this feedback on <span class="hlt">ice</span> age AIS evolution. Here we use a coupled <span class="hlt">ice</span> sheet–sea-level model to investigate the impact of the feedback mechanism on future AIS retreat over centennial and millennial timescales for a range of emission scenarios. We show that the combination of bedrock uplift and sea-surface drop associated with <span class="hlt">ice</span>-sheet retreat significantly reduces AIS <span class="hlt">mass</span> loss relative to a simulation without these effects included. Sensitivity analyses show that the stabilization tends to be greatest for lower emission scenarios and Earth models characterized by a thin elastic lithosphere and low-viscosity upper mantle, as is the case for West Antarctica. PMID:26554381</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JChPh.147i1101M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JChPh.147i1101M"><span>Communication: Hypothetical ultralow-<span class="hlt">density</span> <span class="hlt">ice</span> polymorphs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsui, Takahiro; Hirata, Masanori; Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki</p> <p>2017-09-01</p> <p>More than 300 kinds of porous <span class="hlt">ice</span> structures derived from zeolite frameworks and space fullerenes are examined using classical molecular dynamics simulations. It is found that a hypothetical zeolitic <span class="hlt">ice</span> phase is less dense and more stable than the sparse <span class="hlt">ice</span> structures reported by Huang et al. [Chem. Phys. Lett. 671, 186 (2017)]. In association with the zeolitic <span class="hlt">ice</span> structure, even less dense structures, "aeroices," are proposed. It is found that aeroices are the most stable solid phases of water near the absolute zero temperature under negative pressure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0718L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0718L"><span>Firn Thickness Changes (1982-2015) Driven by SMB from MERRA-2, RACMO2.3, ERA-Int and AVHRR Surface Temperature and the Impacts to Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> Balance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, J.; Medley, B.; Neumann, T.; Smith, B. E.; Luthcke, S. B.; Zwally, H. J.</p> <p>2016-12-01</p> <p>Surface <span class="hlt">mass</span> balance (SMB) data are essential in the derivation of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance. This is because <span class="hlt">ice</span> sheet <span class="hlt">mass</span> change consists of short-term and long-term variations. The short-term variations are directly given by the SMB data. For altimetry based <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance studies, these short-term <span class="hlt">mass</span> changes are converted to firn thickness changes by using a firn densification-elevation model, and then the variations are subtracted from the altimetry measurements to give the long-term <span class="hlt">ice</span> thickness changes that are associated with the <span class="hlt">density</span> of <span class="hlt">ice</span>. So far various SMB data sets such as ERA-Interim, RACMO and MERRA are available and some have been widely used in large number of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance studies. However theses data sets exhibit the clear discrepancies in both random and systematic manner. In this study, we use our time dependent firn densification- elevation model, driven by the SMB data from MERRA-2, RACMO2.3 and ERA-Int for the period of 1982-2015 and the temperature variations from AVHRR for the same period to examine the corresponding firn thickness variations and the impacts to the <span class="hlt">mass</span> changes over the Greenland <span class="hlt">ice</span> sheet. The model was initialized with the1980's climate. Our results show that the relative smaller (centimeter level) differences in the firn thickness driven by the different data set occur at the early stage (1980's) of the model run. As the time progressing, the discrepancies between the SMB data sets accumulate, and the corresponding firn thickness differences quickly become larger with the value > 2m at the end of the period. Although the overall rates for the whole period driven by each of the three data sets are small ranging -0.2 - 0.2 cm a-1 (-3.0-2.7 Gt a-1), the decadal rates can vary greatly with magnitude > 3 cm a-1 and the impact to the Greenland <span class="hlt">mass</span> change exceeds 30 Gt a-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960018485','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960018485"><span>Determination of Local <span class="hlt">Densities</span> in Accreted <span class="hlt">Ice</span> Samples Using X-Rays and Digital Imaging</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Broughton, Howard; Sims, James; Vargas, Mario</p> <p>1996-01-01</p> <p>At the NASA Lewis Research Center's <span class="hlt">Icing</span> Research Tunnel <span class="hlt">ice</span> shapes, similar to those which develop in-flight <span class="hlt">icing</span> conditions, were formed on an airfoil. Under cold room conditions these experimental samples were carefully removed from the airfoil, sliced into thin sections, and x-rayed. The resulting microradiographs were developed and the film digitized using a high resolution scanner to extract fine detail in the radiographs. A procedure was devised to calibrate the scanner and to maintain repeatability during the experiment. The techniques of image acquisition and analysis provide accurate local <span class="hlt">density</span> measurements and reveal the internal characteristics of the accreted <span class="hlt">ice</span> with greater detail. This paper will discuss the methodology by which these samples were prepared with emphasis on the digital imaging techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990071136&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dbalance%2Bsheet','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990071136&hterms=balance+sheet&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dbalance%2Bsheet"><span>Large <span class="hlt">Ice</span> Discharge From the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, Eric</p> <p>1999-01-01</p> <p>The objectives of this work are to measure the <span class="hlt">ice</span> discharge of the Greenland <span class="hlt">Ice</span> Sheet close to the grounding line and/or calving front, and compare the results with <span class="hlt">mass</span> accumulation and ablation in the interior to estimate the <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000070393&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000070393&hterms=3G&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D3G"><span>Measuring Greenland <span class="hlt">Ice</span> <span class="hlt">Mass</span> Variation With Gravity Recovery and the Climate Experiment Gravity and GPS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Xiao-Ping</p> <p>1999-01-01</p> <p>The response of the Greenland <span class="hlt">ice</span> sheet to climate change could significantly alter sea level. The <span class="hlt">ice</span> sheet was much thicker at the last glacial maximum. To gain insight into the global change process and the future trend, it is important to evaluate the <span class="hlt">ice</span> <span class="hlt">mass</span> variation as a function of time and space. The Gravity Recovery and Climate Experiment (GRACE) mission to fly in 2001 for 5 years will measure gravity changes associated with the current <span class="hlt">ice</span> variation and the solid earth's response to past variations. Our objective is to assess the separability of different change sources, accuracy and resolution in the <span class="hlt">mass</span> variation determination by the new gravity data and possible Global Positioning System (GPS) bedrock uplift measurements. We use a reference parameter state that follows a dynamic <span class="hlt">ice</span> model for current <span class="hlt">mass</span> variation and a variant of the Tushingham and Peltier <span class="hlt">ICE</span>-3G deglaciation model for historical deglaciation. The current linear trend is also assumed to have started 5 kyr ago. The Earth model is fixed as preliminary reference Earth model (PREM) with four viscoelastic layers. A discrete Bayesian inverse algorithm is developed employing an isotropic Gaussian a priori covariance function over the <span class="hlt">ice</span> sheet and time. We use data noise predicted by the University of Texas and JPL for major GRACE error sources. A 2 mm/yr uplift uncertainty is assumed for GPS occupation time of 5 years. We then carry out covariance analysis and inverse simulation using GRACE geoid coefficients up to degree 180 in conjunction with a number of GPS uplift rates. Present-day <span class="hlt">ice</span> <span class="hlt">mass</span> variation and historical deglaciation are solved simultaneously over 146 grids of roughly 110 km x 110 km and with 6 time increments of 3 kyr each, along with a common starting epoch of the current trend. For present-day <span class="hlt">ice</span> thickness change, the covariance analysis using GRACE geoid data alone results in a root mean square (RMS) posterior root variance of 2.6 cm/yr, with fairly large a priori</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..MARS16002G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..MARS16002G"><span>Potential Energy Landscape of the Liquid-Liquid Phase Transition in Water and the transformation between Low-<span class="hlt">Density</span> and High-<span class="hlt">Density</span> Amorphous <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giovambattista, N.; Sciortino, F.; Starr, F. W.; Poole, P. H.</p> <p></p> <p>The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics for describing supercooled liquids and glasses. We use the PEL formalism and computer simulations to study the transformation between low-<span class="hlt">density</span> (LDL) and high-<span class="hlt">density</span> liquid (HDL) water, and between low-<span class="hlt">density</span> (LDA) and high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA). We employ the ST2 water model that exhibits a LDL-HDL first-order phase transition and a sharp LDA-HDA transformation, as observed in experiments. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that LDL configurations are located in the same megabasin as LDA, and that HDL configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid and the amorphous <span class="hlt">ice</span> differ. We also study the liquid-to-<span class="hlt">ice</span>-VII first-order phase transition. The PEL properties across this transition are qualitatively similar to the changes found during the LDA-HDA transformation, supporting the interpretation that the LDA-HDA transformation is a first-order-like phase transition between out-of-equilibrium states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880039575&hterms=mass+communication&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dmass%2Bcommunication','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880039575&hterms=mass+communication&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dmass%2Bcommunication"><span>Radio science with Voyager 2 at Uranus - Results on <span class="hlt">masses</span> and <span class="hlt">densities</span> of the planet and five principal satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, J. D.; Campbell, J. K.; Jacobson, R. A.; Sweetnam, D. N.; Taylor, A. H.</p> <p>1987-01-01</p> <p>Phase-coherent Doppler data generated by the Deep Space Network with the radio communication system during the Voyager 2 encounter with Uranus in January 1986, optical navigation data generated by the Voyager Navigation Team with the Voyager 2 imaging system, and ground-based astrometric data obtained over an 8-yr period are compiled and analyzed to determine the <span class="hlt">masses</span> and <span class="hlt">densities</span> of Uranus and its principal satellites. The data-analysis procedures are explained in detail, and the results are presented in tables and graphs. The mean <span class="hlt">density</span> of Uranus is found to be 1.285 + or - 0.001 g/cu cm, whereas the mean uncompressed <span class="hlt">mass</span> of all five satellites is 1.48 + or - 0.06 g/cu cm, or 0.10 g/cu cm above the <span class="hlt">density</span> expected for a homogeneous solar mix of rock, H2O and NH3 <span class="hlt">ice</span>, and CH4 as clathrate hydrate. This difference is tentatively attributed to the presence of 15 <span class="hlt">mass</span> percent of pure graphite, which would provide the thermal conductivity required to keep the satellites cold and undifferentiated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26932187','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26932187"><span>Colonization of maritime glacier <span class="hlt">ice</span> by bdelloid Rotifera.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shain, Daniel H; Halldórsdóttir, Katrín; Pálsson, Finnur; Aðalgeirsdóttir, Guðfinna; Gunnarsson, Andri; Jónsson, Þorsteinn; Lang, Shirley A; Pálsson, Hlynur Skagfjörð; Steinþórssson, Sveinbjörn; Arnason, Einar</p> <p>2016-05-01</p> <p>Very few animal taxa are known to reside permanently in glacier <span class="hlt">ice</span>/snow. Here we report the widespread colonization of Icelandic glaciers and <span class="hlt">ice</span> fields by species of bdelloid Rotifera. Specimens were collected within the accumulation zones of Langjökull and Vatnajökull <span class="hlt">ice</span> caps, among the largest European <span class="hlt">ice</span> <span class="hlt">masses</span>. Rotifers reached <span class="hlt">densities</span> up to ∼100 individuals per liter-equivalent of glacier <span class="hlt">ice</span>/snow, and were freeze-tolerant. Phylogenetic analyses indicate that glacier rotifers are polyphyletic, with independent ancestries occurring within the Pleistocene. Collectively, these data identify a previously undescribed environmental niche for bdelloid rotifers and suggest their presence in comparable habitats worldwide. Copyright © 2016 Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G21B0875K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G21B0875K"><span>Exploring the effect of East Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> loss on GIA-induced horizontal bedrock motions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konfal, S. A.; Whitehouse, P. L.; Hermans, T.; van der Wal, W.; Wilson, T. J.; Bevis, M. G.; Kendrick, E. C.; Dalziel, I.; Smalley, R., Jr.</p> <p>2017-12-01</p> <p><span class="hlt">Ice</span> history inputs used in Antarctic models of GIA include major centers of <span class="hlt">ice</span> <span class="hlt">mass</span> loss in West Antarctica. In the Transantarctic Mountains (TAM) region spanning the boundary between East and West Antarctica, horizontal crustal motions derived from GPS observations from the Antarctic Network (ANET) component of the Polar Earth Observing Network (POLENET) are towards these West Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> centers, opposite to the pattern of radial crustal motion expected in an unloading scenario. We investigate alternative <span class="hlt">ice</span> history and earth structure inputs to GIA models in an attempt to reproduce observed crustal motions in the region. The W12 <span class="hlt">ice</span> history model is altered to create scenarios including <span class="hlt">ice</span> unloading in the Wilkes Subglacial Basin based on available glaciological records. These altered <span class="hlt">ice</span> history models, along with the unmodified W12 <span class="hlt">ice</span> history model, are coupled with 60 radially varying (1D) earth model combinations, including approximations of optimal earth profiles identified in published GIA models. The resulting model-predicted motions utilizing both the modified and unmodified <span class="hlt">ice</span> history models fit ANET GPS-derived crustal motions in the northern TAM region for a suite of earth model combinations. Further south, where the influence of simulated Wilkes unloading is weakest and West Antarctic unloading is strongest, observed and predicted motions do not agree. The influence of simulated Wilkes <span class="hlt">ice</span> unloading coupled with laterally heterogeneous earth models is also investigated. The resulting model-predicted motions do not differ significantly between the original W12 and W12 with simulated Wilkes unloading <span class="hlt">ice</span> histories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1390292-diffusive-dynamics-during-high-low-density-transition-amorphous-ice','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1390292-diffusive-dynamics-during-high-low-density-transition-amorphous-ice"><span>Diffusive dynamics during the high-to-low <span class="hlt">density</span> transition in amorphous <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Perakis, Fivos; Amann-Winkel, Katrin; Lehmkuhler, Felix; ...</p> <p>2017-06-26</p> <p>Water exists in high- and low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-<span class="hlt">density</span> liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-<span class="hlt">density</span> transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-<span class="hlt">density</span> transition in amorphous <span class="hlt">ice</span> at 1 bar. By analyzing the structure factor and the radial distributionmore » function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-<span class="hlt">density</span> form at 130 K, but remains diffusive. In conclusion, the diffusive character of both the high- and low-<span class="hlt">density</span> forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1390292','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1390292"><span>Diffusive dynamics during the high-to-low <span class="hlt">density</span> transition in amorphous <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Perakis, Fivos; Amann-Winkel, Katrin; Lehmkuhler, Felix</p> <p></p> <p>Water exists in high- and low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-<span class="hlt">density</span> liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-<span class="hlt">density</span> transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-<span class="hlt">density</span> transition in amorphous <span class="hlt">ice</span> at 1 bar. By analyzing the structure factor and the radial distributionmore » function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-<span class="hlt">density</span> form at 130 K, but remains diffusive. In conclusion, the diffusive character of both the high- and low-<span class="hlt">density</span> forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCry....8..743G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCry....8..743G"><span>Empirical estimation of present-day Antarctic glacial isostatic adjustment and <span class="hlt">ice</span> <span class="hlt">mass</span> change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunter, B. C.; Didova, O.; Riva, R. E. M.; Ligtenberg, S. R. M.; Lenaerts, J. T. M.; King, M. A.; van den Broeke, M. R.; Urban, T.</p> <p>2014-04-01</p> <p>This study explores an approach that simultaneously estimates Antarctic <span class="hlt">mass</span> balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new <span class="hlt">Ice</span>, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related <span class="hlt">mass</span> change estimates for the entire Antarctic <span class="hlt">ice</span> sheet ranged from 53 to 103 Gt yr-1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr-1. Over the time frame February 2003-October 2009, the corresponding <span class="hlt">ice</span> <span class="hlt">mass</span> change showed an average value of -100 ± 44 Gt yr-1 (EA: 5 ± 38, WA: -105 ± 22), consistent with other recent estimates in the literature, with regional <span class="hlt">mass</span> loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and <span class="hlt">ice</span> <span class="hlt">mass</span> change, particularly with respect to determining more reliable uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.7328C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.7328C"><span><span class="hlt">Mass</span> balance reassessment of glaciers draining into the Abbot and Getz <span class="hlt">Ice</span> Shelves of West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuter, S. J.; Martín-Español, A.; Wouters, B.; Bamber, J. L.</p> <p>2017-07-01</p> <p>We present a reassessment of input-output method <span class="hlt">ice</span> <span class="hlt">mass</span> budget estimates for the Abbot and Getz regions of West Antarctica using CryoSat-2-derived <span class="hlt">ice</span> thickness estimates. The <span class="hlt">mass</span> budget is 8 ± 6 Gt yr-1 and 5 ± 17 Gt yr-1 for the Abbot and Getz sectors, respectively, for the period 2006-2008. Over the Abbot region, our results resolve a previous discrepancy with elevation rates from altimetry, due to a previous 30% overestimation of <span class="hlt">ice</span> thickness. For the Getz sector, our results are at the more positive bound of estimates from other techniques. Grounding line velocity increases up to 20% between 2007 and 2014 alongside mean elevation rates of -0.67 ± 0.13 m yr-1 between 2010 and 2013 indicate the onset of a dynamic thinning signal. Mean snowfall trends of -0.33 m yr-1 water equivalent since 2006 indicate recent <span class="hlt">mass</span> trends are driven by both <span class="hlt">ice</span> dynamics and surface processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017M%26PS...52.1505H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017M%26PS...52.1505H"><span>Hypervelocity impacts into <span class="hlt">ice</span>-topped layered targets: Investigating the effects of <span class="hlt">ice</span> crust thickness and subsurface <span class="hlt">density</span> on crater morphology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harriss, Kathryn H.; Burchell, Mark J.</p> <p>2017-07-01</p> <p>Many bodies in the outer solar system are theorized to have an <span class="hlt">ice</span> shell with a different subsurface material below, be it chondritic, regolith, or a subsurface ocean. This layering can have a significant influence on the morphology of impact craters. Accordingly, we have undertaken laboratory hypervelocity impact experiments on a range of multilayered targets, with interiors of water, sand, and basalt. Impact experiments were undertaken using impact speeds in the range of 0.8-5.3 km s-1, a 1.5 mm Al ball bearing projectile, and an impact incidence of 45°. The surface <span class="hlt">ice</span> crust had a thickness between 5 and 50 mm, i.e., some 3-30 times the projectile diameter. The thickness of the <span class="hlt">ice</span> crust as well as the nature of the subsurface layer (liquid, well consolidated, etc.) have a marked effect on the morphology of the resulting impact crater, with thicker <span class="hlt">ice</span> producing a larger crater diameter (at a given impact velocity), and the crater diameter scaling with impact speed to the power 0.72 for semi-infinite <span class="hlt">ice</span>, but with 0.37 for thin <span class="hlt">ice</span>. The <span class="hlt">density</span> of the subsurface material changes the structure of the crater, with flat crater floors if there is a dense, well-consolidated subsurface layer (basalt) or steep, narrow craters if there is a less cohesive subsurface (sand). The associated faulting in the <span class="hlt">ice</span> surface is also dependent on <span class="hlt">ice</span> thickness and the substrate material. We find that the <span class="hlt">ice</span> layer (in impacts at 5 km s-1) is effectively semi-infinite if its thickness is more than 15.5 times the projectile diameter. Below this, the crater diameter is reduced by 4% for each reduction in <span class="hlt">ice</span> layer thickness equal to the impactor diameter. Crater depth is also affected. In the <span class="hlt">ice</span> thickness region, 7-15.5 times the projectile diameter, the crater shape in the <span class="hlt">ice</span> is modified even when the subsurface layer is not penetrated. For <span class="hlt">ice</span> thicknesses, <7 times the projectile diameter, the <span class="hlt">ice</span> layer is breached, but the nature of the resulting crater depends heavily on the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918364H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918364H"><span>Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> Balance Buoys (IMBs): First Results from a Data Processing Intercomparison Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoppmann, Mario; Tiemann, Louisa; Itkin, Polona</p> <p>2017-04-01</p> <p>IMBs are autonomous instruments able to continuously monitor the growth and melt of sea <span class="hlt">ice</span> and its snow cover at a single point on an <span class="hlt">ice</span> floe. Complementing field expeditions, remote sensing observations and modelling studies, these in-situ data are crucial to assess the <span class="hlt">mass</span> balance and seasonal evolution of sea <span class="hlt">ice</span> and snow in the polar oceans. Established subtypes of IMBs combine coarse-resolution temperature profiles through air, snow, <span class="hlt">ice</span> and ocean with ultrasonic pingers to detect snow accumulation and <span class="hlt">ice</span> thermodynamic growth. Recent technological advancements enable the use of high-resolution temperature chains, which are also able to identify the surrounding medium through a „heating cycle". The temperature change during this heating cycle provides additional information on the internal properties and processes of the <span class="hlt">ice</span>. However, a unified data processing technique to reliably and accurately determine sea <span class="hlt">ice</span> thickness and snow depth from this kind of data is still missing, and an unambiguous interpretation remains a challenge. Following the need to improve techniques for remotely measuring sea <span class="hlt">ice</span> <span class="hlt">mass</span> balance, an international IMB working group has recently been established. The main goals are 1) to coordinate IMB deployments, 2) to enhance current IMB data processing and -interpretation techniques, and 3) to provide standardized IMB data products to a broader community. Here we present first results from two different data processing algorithms, applied to selected IMB datasets from the Arctic and Antarctic. Their performance with regard to sea <span class="hlt">ice</span> thickness and snow depth retrieval is evaluated, and an uncertainty is determined. Although several challenges and caveats in IMB data processing and -interpretation are found, such datasets bear great potential and yield plenty of useful information about sea <span class="hlt">ice</span> properties and processes. It is planned to include many more algorithms from contributors within the working group, and we explicitly invite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26672555','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26672555"><span>Spatial and temporal distribution of <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet since AD 1900.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kjeldsen, Kristian K; Korsgaard, Niels J; Bjørk, Anders A; Khan, Shfaqat A; Box, Jason E; Funder, Svend; Larsen, Nicolaj K; Bamber, Jonathan L; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S; Willerslev, Eske; Kjær, Kurt H</p> <p>2015-12-17</p> <p>The response of the Greenland <span class="hlt">Ice</span> Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of <span class="hlt">ice</span> <span class="hlt">mass</span> changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial <span class="hlt">ice</span> <span class="hlt">mass</span> loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little <span class="hlt">Ice</span> Age at the end of the nineteenth century. We estimate the total <span class="hlt">ice</span> <span class="hlt">mass</span> loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface <span class="hlt">mass</span> balance models we partition the <span class="hlt">mass</span> balance into a term for surface <span class="hlt">mass</span> balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface <span class="hlt">mass</span> balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Natur.528..396K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Natur.528..396K"><span>Spatial and temporal distribution of <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet since AD 1900</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kjeldsen, Kristian K.; Korsgaard, Niels J.; Bjørk, Anders A.; Khan, Shfaqat A.; Box, Jason E.; Funder, Svend; Larsen, Nicolaj K.; Bamber, Jonathan L.; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S.; Willerslev, Eske; Kjær, Kurt H.</p> <p>2015-12-01</p> <p>The response of the Greenland <span class="hlt">Ice</span> Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of <span class="hlt">ice</span> <span class="hlt">mass</span> changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial <span class="hlt">ice</span> <span class="hlt">mass</span> loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little <span class="hlt">Ice</span> Age at the end of the nineteenth century. We estimate the total <span class="hlt">ice</span> <span class="hlt">mass</span> loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface <span class="hlt">mass</span> balance models we partition the <span class="hlt">mass</span> balance into a term for surface <span class="hlt">mass</span> balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface <span class="hlt">mass</span> balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhRvL.108v5901H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhRvL.108v5901H"><span>Relaxation Time of High-<span class="hlt">Density</span> Amorphous <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Handle, Philip H.; Seidl, Markus; Loerting, Thomas</p> <p>2012-06-01</p> <p>Amorphous water plays a fundamental role in astrophysics, cryoelectron microscopy, hydration of matter, and our understanding of anomalous liquid water properties. Yet, the characteristics of the relaxation processes taking place in high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA) are unknown. We here reveal that the relaxation processes in HDA at 110-135 K at 0.1-0.2 GPa are of collective and global nature, resembling the alpha relaxation in glassy material. Measured relaxation times suggest liquid-like relaxation characteristics in the vicinity of the crystallization temperature at 145 K. By carefully relaxing pressurized HDA for several hours at 135 K, we produce a state that is closer to the ideal glass state than all HDA states discussed so far in literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EPSC...11.1010K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EPSC...11.1010K"><span>Reproducing impact ionization <span class="hlt">mass</span> spectra of E and F ring <span class="hlt">ice</span> grains at different impact speeds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klenner, F.; Reviol, R.; Postberg, F.</p> <p>2017-09-01</p> <p>As impact speeds of E and F ring <span class="hlt">ice</span> grains impinging onto the target of impact ionization <span class="hlt">mass</span> spectrometers in space can vary greatly, the resulting cationic or anionic <span class="hlt">mass</span> spectra can have very different appearances. The <span class="hlt">mass</span> spectra can be accurately reproduced with an analog experimental setup IR-FL-MALDI-ToF-MS (Infrared Free Liquid Matrix Assisted Laser Desorption and Ionization Time of Flight <span class="hlt">Mass</span> Spectrometry). We compare <span class="hlt">mass</span> spectra of E and F ring <span class="hlt">ice</span> grains taken by the Cosmic Dust Analyzer (CDA) onboard Cassini recorded at different impact speeds with our analog spectra and prove the capability of the analog experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0728S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0728S"><span>On the Utilization of <span class="hlt">Ice</span> Flow Models and Uncertainty Quantification to Interpret the Impact of Surface Radiation Budget Errors on Estimates of Greenland <span class="hlt">Ice</span> Sheet Surface <span class="hlt">Mass</span> Balance and Regional Estimates of <span class="hlt">Mass</span> Balance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlegel, N.; Larour, E. Y.; Gardner, A. S.; Lang, C.; Miller, C. E.; van den Broeke, M. R.</p> <p>2016-12-01</p> <p>How Greenland <span class="hlt">ice</span> flow may respond to future increases in surface runoff and to increases in the frequency of extreme melt events is unclear, as it requires detailed comprehension of Greenland surface climate and the <span class="hlt">ice</span> sheet's sensitivity to associated uncertainties. With established uncertainty quantification tools run within the framework of <span class="hlt">Ice</span> Sheet System Model (ISSM), we conduct decadal-scale forward modeling experiments to 1) quantify the spatial resolution needed to effectively force distinct components of the surface radiation budget, and subsequently surface <span class="hlt">mass</span> balance (SMB), in various regions of the <span class="hlt">ice</span> sheet and 2) determine the dynamic response of Greenland <span class="hlt">ice</span> flow to variations in components of the net radiation budget. The Glacier Energy and <span class="hlt">Mass</span> Balance (GEMB) software is a column surface model (1-D) that has recently been embedded as a module within ISSM. Using the ISSM-GEMB framework, we perform sensitivity analyses to determine how perturbations in various components of the surface radiation budget affect model output; these model experiments allow us predict where and on what spatial scale the <span class="hlt">ice</span> sheet is likely to dynamically respond to changes in these parameters. Preliminary results suggest that SMB should be forced at at least a resolution of 23 km to properly capture dynamic <span class="hlt">ice</span> response. In addition, Monte-Carlo style sampling analyses reveals that the areas with the largest uncertainty in <span class="hlt">mass</span> flux are located near the equilibrium line altitude (ELA), upstream of major outlet glaciers in the North and West of the <span class="hlt">ice</span> sheet. Sensitivity analysis indicates that these areas are also the most vulnerable on the <span class="hlt">ice</span> sheet to persistent, far-field shifts in SMB, suggesting that continued warming, and upstream shift in the ELA, are likely to result in increased velocities, and consequentially SMB-induced thinning upstream of major outlet glaciers. Here, we extend our investigation to consider various components of the surface radiation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017DPS....4911019D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017DPS....4911019D"><span>Bayesian modeling of the <span class="hlt">mass</span> and <span class="hlt">density</span> of asteroids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dotson, Jessie L.; Mathias, Donovan</p> <p>2017-10-01</p> <p><span class="hlt">Mass</span> and <span class="hlt">density</span> are two of the fundamental properties of any object. In the case of near earth asteroids, knowledge about the <span class="hlt">mass</span> of an asteroid is essential for estimating the risk due to (potential) impact and planning possible mitigation options. The <span class="hlt">density</span> of an asteroid can illuminate the structure of the asteroid. A low <span class="hlt">density</span> can be indicative of a rubble pile structure whereas a higher <span class="hlt">density</span> can imply a monolith and/or higher metal content. The damage resulting from an impact of an asteroid with Earth depends on its interior structure in addition to its total <span class="hlt">mass</span>, and as a result, <span class="hlt">density</span> is a key parameter to understanding the risk of asteroid impact. Unfortunately, measuring the <span class="hlt">mass</span> and <span class="hlt">density</span> of asteroids is challenging and often results in measurements with large uncertainties. In the absence of <span class="hlt">mass</span> / <span class="hlt">density</span> measurements for a specific object, understanding the range and distribution of likely values can facilitate probabilistic assessments of structure and impact risk. Hierarchical Bayesian models have recently been developed to investigate the <span class="hlt">mass</span> - radius relationship of exoplanets (Wolfgang, Rogers & Ford 2016) and to probabilistically forecast the <span class="hlt">mass</span> of bodies large enough to establish hydrostatic equilibrium over a range of 9 orders of magnitude in <span class="hlt">mass</span> (from planemos to main sequence stars; Chen & Kipping 2017). Here, we extend this approach to investigate the <span class="hlt">mass</span> and <span class="hlt">densities</span> of asteroids. Several candidate Bayesian models are presented, and their performance is assessed relative to a synthetic asteroid population. In addition, a preliminary Bayesian model for probablistically forecasting <span class="hlt">masses</span> and <span class="hlt">densities</span> of asteroids is presented. The forecasting model is conditioned on existing asteroid data and includes observational errors, hyper-parameter uncertainties and intrinsic scatter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...819...83W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...819...83W"><span>Revised <span class="hlt">Masses</span> and <span class="hlt">Densities</span> of the Planets around Kepler-10</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weiss, Lauren M.; Rogers, Leslie A.; Isaacson, Howard T.; Agol, Eric; Marcy, Geoffrey W.; Rowe, Jason F.; Kipping, David; Fulton, Benjamin J.; Lissauer, Jack J.; Howard, Andrew W.; Fabrycky, Daniel</p> <p>2016-03-01</p> <p>Determining which small exoplanets have stony-iron compositions is necessary for quantifying the occurrence of such planets and for understanding the physics of planet formation. Kepler-10 hosts the stony-iron world Kepler-10b, and also contains what has been reported to be the largest solid silicate-<span class="hlt">ice</span> planet, Kepler-10c. Using 220 radial velocities (RVs), including 72 precise RVs from Keck-HIRES of which 20 are new from 2014 to 2015, and 17 quarters of Kepler photometry, we obtain the most complete picture of the Kepler-10 system to date. We find that Kepler-10b ({R}{{p}}=1.47 {R}\\oplus ) has <span class="hlt">mass</span> 3.72\\quad +/- \\quad 0.42\\quad {M}\\oplus and <span class="hlt">density</span> 6.46\\quad +/- \\quad 0.73\\quad {{g}} {{cm}}-3. Modeling the interior of Kepler-10b as an iron core overlaid with a silicate mantle, we find that the iron core constitutes 0.17 ± 0.11 of the planet <span class="hlt">mass</span>. For Kepler-10c ({R}{{p}}=2.35 {R}\\oplus ) we measure <span class="hlt">mass</span> 13.98\\quad +/- \\quad 1.79\\quad {M}\\oplus and <span class="hlt">density</span> 5.94\\quad +/- \\quad 0.76\\quad {{g}} {{cm}}-3, significantly lower than the <span class="hlt">mass</span> computed in Dumusque et al. (17.2+/- 1.9 {M}\\oplus ). Our <span class="hlt">mass</span> measurement of Kepler-10c rules out a pure stony-iron composition. Internal compositional modeling reveals that at least 10% of the radius of Kepler-10c is a volatile envelope composed of hydrogen-helium (0.2% of the <span class="hlt">mass</span>, 16% of the radius) or super-ionic water (28% of the <span class="hlt">mass</span>, 29% of the radius). However, we note that analysis of only HIRES data yields a higher <span class="hlt">mass</span> for planet b and a lower <span class="hlt">mass</span> for planet c than does analysis of the HARPS-N data alone, with the <span class="hlt">mass</span> estimates for Kepler-10 c being formally inconsistent at the 3σ level. Moreover, dividing the data for each instrument into two parts also leads to somewhat inconsistent measurements for the <span class="hlt">mass</span> of planet c derived from each observatory. Together, this suggests that time-correlated noise is present and that the uncertainties in the <span class="hlt">masses</span> of the planets (especially planet c) likely</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..12210694H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..12210694H"><span>High-Latitude Neutral <span class="hlt">Mass</span> <span class="hlt">Density</span> Maxima</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, C. Y.; Huang, Y.; Su, Y.-J.; Huang, T.; Sutton, E. K.</p> <p>2017-10-01</p> <p>Recent studies have reported that thermospheric effects due to solar wind driving can be observed poleward of auroral latitudes. In these papers, the measured neutral <span class="hlt">mass</span> <span class="hlt">density</span> perturbations appear as narrow, localized maxima in the cusp and polar cap. They conclude that Joule heating below the spacecraft is the cause of the <span class="hlt">mass</span> <span class="hlt">density</span> increases, which are sometimes associated with local field-aligned current structures, but not always. In this paper we investigate neutral <span class="hlt">mass</span> <span class="hlt">densities</span> measured by accelerometers on the CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) spacecraft from launch until years 2010 (CHAMP) and 2012 (GRACE), approximately 10 years of observations from each satellite. We extract local maxima in neutral <span class="hlt">mass</span> <span class="hlt">densities</span> over the background using a smoothing window with size of one quarter of the orbit. The maxima have been analyzed for each year and also for the duration of each set of satellite observations. We show where they occur, under what solar wind conditions, and their relation to magnetic activity. The region with the highest frequency of occurrence coincides approximately with the cusp and mantle, with little direct evidence of an auroral zone source. Our conclusions agree with the "hot polar cap" observations that have been reported and studied in the past.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P31A2080G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P31A2080G"><span>Do Europa's Mountains Have Roots? Erosion of Topography at the <span class="hlt">Ice</span>-Water Interface via the "<span class="hlt">Ice</span> Pump"</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goodman, J. C.</p> <p>2016-12-01</p> <p>Are topographic features on the surface of Europa and other icy worlds isostatically compensated by variations in shell thickness (Airy isostasy)? This is only possible if variations in shell thickness can remain stable over geologic time. Here we show that melting and freezing driven by the pressure dependence of the melting point of water - the "<span class="hlt">ice</span> pump" - can rapidly erase topography at the <span class="hlt">ice</span>/water interface. We consider <span class="hlt">ice</span> pumps driven by both tidal action and buoyancy-driven flow. We first show that as tidal action drives the ocean up and down along a sloping interface, <span class="hlt">ice</span> will be melted from areas where it's thickest and deposited where the <span class="hlt">ice</span> is thinnest. We show that this process causes the <span class="hlt">ice</span> interface topography to relax according to a simple "diffusion" linear partial differential equation. We estimate that a 10-km-wide topographic feature would be erased by the tidal <span class="hlt">ice</span> pump in 3000 years if Europa's tidal current amplitude is 1 cm/s; however, this timescale is inversely proportional to the cube of the tidal velocity! Next, we consider an <span class="hlt">ice</span> pump powered by ascent of meltwater along a sloping <span class="hlt">ice</span>-water interface. We consider layer-averaged budgets for heat, <span class="hlt">mass</span>, and momentum, along with turbulent mixing of the meltwater layer with underlying seawater via a Richardson number dependent entrainment process, and use these to estimate the thickness and <span class="hlt">mass</span> flux of the meltwater layer. From this we estimate the rate of melting and freezing at the interface. These two <span class="hlt">ice</span> pump processes combine with the glacial flow of warm basal <span class="hlt">ice</span> to rapidly flatten out any variations in the height of the <span class="hlt">ice</span>-water interface: Europa's <span class="hlt">ice</span>/water interface may be perfectly flat! If so, topography at Europa's surface can only be supported by variations in <span class="hlt">density</span> of the shell or the strength of the brittle surface <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000279','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000279"><span>A Range Correction for Icesat and Its Potential Impact on <span class="hlt">Ice</span>-sheet <span class="hlt">Mass</span> Balance Studies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Borsa, A. A.; Moholdt, G.; Fricker, H. A.; Brunt, Kelly M.</p> <p>2014-01-01</p> <p>We report on a previously undocumented range error in NASA's <span class="hlt">Ice</span>, Cloud and land Elevation Satellite (ICESat) that degrades elevation precision and introduces a small but significant elevation trend over the ICESat mission period. This range error (the Gaussian-Centroid or 'G-C'offset) varies on a shot-to-shot basis and exhibits increasing scatter when laser transmit energies fall below 20 mJ. Although the G-C offset is uncorrelated over periods less than1 day, it evolves over the life of each of ICESat's three lasers in a series of ramps and jumps that give rise to spurious elevation trends of -0.92 to -1.90 cm yr(exp -1), depending on the time period considered. Using ICESat data over the Ross and Filchner-Ronne <span class="hlt">ice</span> shelves we show that (1) the G-C offset introduces significant biases in <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> balance estimates, and (2) the <span class="hlt">mass</span> balance bias can vary between regions because of different temporal samplings of ICESat.We can reproduce the effect of the G-C offset over these two <span class="hlt">ice</span> shelves by fitting trends to sample-weighted mean G-C offsets for each campaign, suggesting that it may not be necessary to fully repeat earlier ICESat studies to determine the impact of the G-C offset on <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> balance estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRF..118..667S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRF..118..667S"><span>Decadal-scale sensitivity of Northeast Greenland <span class="hlt">ice</span> flow to errors in surface <span class="hlt">mass</span> balance using ISSM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlegel, N.-J.; Larour, E.; Seroussi, H.; Morlighem, M.; Box, J. E.</p> <p>2013-06-01</p> <p>The behavior of the Greenland <span class="hlt">Ice</span> Sheet, which is considered a major contributor to sea level changes, is best understood on century and longer time scales. However, on decadal time scales, its response is less predictable due to the difficulty of modeling surface climate, as well as incomplete understanding of the dynamic processes responsible for <span class="hlt">ice</span> flow. Therefore, it is imperative to understand how modeling advancements, such as increased spatial resolution or more comprehensive <span class="hlt">ice</span> flow equations, might improve projections of <span class="hlt">ice</span> sheet response to climatic trends. Here we examine how a finely resolved climate forcing influences a high-resolution <span class="hlt">ice</span> stream model that considers longitudinal stresses. We simulate <span class="hlt">ice</span> flow using a two-dimensional Shelfy-Stream Approximation implemented within the <span class="hlt">Ice</span> Sheet System Model (ISSM) and use uncertainty quantification tools embedded within the model to calculate the sensitivity of <span class="hlt">ice</span> flow within the Northeast Greenland <span class="hlt">Ice</span> Stream to errors in surface <span class="hlt">mass</span> balance (SMB) forcing. Our results suggest that the model tends to smooth <span class="hlt">ice</span> velocities even when forced with extreme errors in SMB. Indeed, errors propagate linearly through the model, resulting in discharge uncertainty of 16% or 1.9 Gt/yr. We find that <span class="hlt">mass</span> flux is most sensitive to local errors but is also affected by errors hundreds of kilometers away; thus, an accurate SMB map of the entire basin is critical for realistic simulation. Furthermore, sensitivity analyses indicate that SMB forcing needs to be provided at a resolution of at least 40 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P53H..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P53H..07W"><span><span class="hlt">Mass</span> Fluxes of <span class="hlt">Ice</span> and Oxygen Across the Entire Lid of Lake Vostok from Observations of Englacial Radiowave Attenuation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winebrenner, D. P.; Kintner, P. M. S.; MacGregor, J. A.</p> <p>2017-12-01</p> <p>Over deep Antarctic subglacial lakes, spatially varying <span class="hlt">ice</span> thickness and the pressure-dependent melting point of <span class="hlt">ice</span> result in areas of melting and accretion at the <span class="hlt">ice</span>-water interface, i.e., the lake lid. These <span class="hlt">ice</span> <span class="hlt">mass</span> fluxes drive lake circulation and, because basal Antarctic <span class="hlt">ice</span> contains air-clathrate, affect the input of oxygen to the lake, with implications for subglacial life. Inferences of melting and accretion from radar-layer tracking and geodesy are limited in spatial coverage and resolution. Here we develop a new method to estimate rates of accretion, melting, and the resulting oxygen input at a lake lid, using airborne radar data over Lake Vostok together with <span class="hlt">ice</span>-temperature and chemistry data from the Vostok <span class="hlt">ice</span> core. Because the lake lid is a coherent reflector of known reflectivity (at our radar frequency), we can infer depth-averaged radiowave attenuation in the <span class="hlt">ice</span>, with spatial resolution 1 km along flight lines. Spatial variation in attenuation depends mostly on variation in <span class="hlt">ice</span> temperature near the lid, which in turn varies strongly with <span class="hlt">ice</span> <span class="hlt">mass</span> flux at the lid. We model <span class="hlt">ice</span> temperature versus depth with <span class="hlt">ice</span> <span class="hlt">mass</span> flux as a parameter, thus linking that flux to (observed) depth-averaged attenuation. The resulting map of melt- and accretion-rates independently reproduces features known from earlier studies, but now covers the entire lid. We find that accretion is dominant when integrated over the lid, with an <span class="hlt">ice</span> imbalance of 0.05 to 0.07 km3 a-1, which is robust against uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33D1227B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33D1227B"><span>Modelling the contribution of supraglacial <span class="hlt">ice</span> cliffs to the <span class="hlt">mass</span>-balance of glaciers in the Langtang catchment, Nepalese Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buri, P.; Steiner, J. F.; Miles, E.; Ragettli, S.; Pellicciotti, F.</p> <p>2017-12-01</p> <p>Supraglacial cliffs are typical surface features of debris-covered glaciers worldwide, affecting surface evolution, and <span class="hlt">mass</span> balance by providing a direct <span class="hlt">ice</span>-atmosphere interface where melt rates can be very high. As a result, <span class="hlt">ice</span> cliffs act as windows of energy transfer from the atmosphere to the <span class="hlt">ice</span>, and enhance melt and <span class="hlt">mass</span> losses of otherwise insulated <span class="hlt">ice</span>. However, their contribution to glacier <span class="hlt">mass</span> balance has never been quantified at the glacier scale, and all inference has been obtained from upscaling results of point-scale models or observations at select individual cliffs. Here we use a 3D, physically-based backwasting model to estimate the volume losses associated with the melting and backwasting of supraglacial <span class="hlt">ice</span> cliffs for the entire debris-covered glacier area of the Langtang catchment. We estimate <span class="hlt">mass</span> losses for the 2014 melt season and compare them to recent values of glacier <span class="hlt">mass</span> balance determined from geodetic and numerical modelling approached. Cliff outlines and topography are derived from high-resolution stereo SPOT6-imagery from April 2014. Meteorological data to force the model are provided by automatic weather stations on- and off-glacier within the valley. The model simulates <span class="hlt">ice</span> cliff backwasting by considering the cliff-atmosphere energy-balance, reburial by debris and the effects of adjacent ponds. In the melt season of 2014, cliffs' distribution and patterns of <span class="hlt">mass</span> losses vary considerably from glacier to glacier, and we relate rates of volume loss to both glaciers' and cliffs' characteristics. Only cliffs with a northerly aspect account for substantial losses. Uncertainty in our estimates is due to the quality of the stereo DEM, uncertainties in the cliff delineation and the fact that we use a conservative approach to cliff delineation and discard very small cliffs and those for which uncertainty in topography is high. Despite these uncertainties, our work presents the first estimate of the importance of supraglacial <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000872','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000872"><span><span class="hlt">Icing</span> Analysis of a Swept NACA 0012 Wing Using LEWICE3D Version 3.48</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bidwell, Colin S.</p> <p>2014-01-01</p> <p><span class="hlt">Icing</span> calculations were performed for a NACA 0012 swept wing tip using LEWICE3D Version 3.48 coupled with the ANSYS CFX flow solver. The calculated <span class="hlt">ice</span> shapes were compared to experimental data generated in the NASA Glenn <span class="hlt">Icing</span> Research Tunnel (IRT). The IRT tests were designed to test the performance of the LEWICE3D <span class="hlt">ice</span> void <span class="hlt">density</span> model which was developed to improve the prediction of swept wing <span class="hlt">ice</span> shapes. <span class="hlt">Icing</span> tests were performed for a range of temperatures at two different droplet inertia parameters and two different sweep angles. The predicted <span class="hlt">mass</span> agreed well with the experiment with an average difference of 12%. The LEWICE3D <span class="hlt">ice</span> void <span class="hlt">density</span> model under-predicted void <span class="hlt">density</span> by an average of 30% for the large inertia parameter cases and by 63% for the small inertia parameter cases. This under-prediction in void <span class="hlt">density</span> resulted in an over-prediction of <span class="hlt">ice</span> area by an average of 115%. The LEWICE3D <span class="hlt">ice</span> void <span class="hlt">density</span> model produced a larger average area difference with experiment than the standard LEWICE <span class="hlt">density</span> model, which doesn't account for the voids in the swept wing <span class="hlt">ice</span> shape, (115% and 75% respectively) but it produced <span class="hlt">ice</span> shapes which were deemed more appropriate because they were conservative (larger than experiment). Major contributors to the overly conservative <span class="hlt">ice</span> shape predictions were deficiencies in the leading edge heat transfer and the sensitivity of the void <span class="hlt">ice</span> <span class="hlt">density</span> model to the particle inertia parameter. The scallop features present on the <span class="hlt">ice</span> shapes were thought to generate interstitial flow and horse shoe vortices which enhance the leading edge heat transfer. A set of changes to improve the leading edge heat transfer and the void <span class="hlt">density</span> model were tested. The changes improved the <span class="hlt">ice</span> shape predictions considerably. More work needs to be done to evaluate the performance of these modifications for a wider range of geometries and <span class="hlt">icing</span> conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000867','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000867"><span><span class="hlt">Icing</span> Analysis of a Swept NACA 0012 Wing Using LEWICE3D Version 3.48</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bidwell, Colin S.</p> <p>2014-01-01</p> <p><span class="hlt">Icing</span> calculations were performed for a NACA 0012 swept wing tip using LEWICE3D Version 3.48 coupled with the ANSYS CFX flow solver. The calculated <span class="hlt">ice</span> shapes were compared to experimental data generated in the NASA Glenn <span class="hlt">Icing</span> Research Tunnel (IRT). The IRT tests were designed to test the performance of the LEWICE3D <span class="hlt">ice</span> void <span class="hlt">density</span> model which was developed to improve the prediction of swept wing <span class="hlt">ice</span> shapes. <span class="hlt">Icing</span> tests were performed for a range of temperatures at two different droplet inertia parameters and two different sweep angles. The predicted <span class="hlt">mass</span> agreed well with the experiment with an average difference of 12%. The LEWICE3D <span class="hlt">ice</span> void <span class="hlt">density</span> model under-predicted void <span class="hlt">density</span> by an average of 30% for the large inertia parameter cases and by 63% for the small inertia parameter cases. This under-prediction in void <span class="hlt">density</span> resulted in an over-prediction of <span class="hlt">ice</span> area by an average of 115%. The LEWICE3D <span class="hlt">ice</span> void <span class="hlt">density</span> model produced a larger average area difference with experiment than the standard LEWICE <span class="hlt">density</span> model, which doesn't account for the voids in the swept wing <span class="hlt">ice</span> shape, (115% and 75% respectively) but it produced <span class="hlt">ice</span> shapes which were deemed more appropriate because they were conservative (larger than experiment). Major contributors to the overly conservative <span class="hlt">ice</span> shape predictions were deficiencies in the leading edge heat transfer and the sensitivity of the void <span class="hlt">ice</span> <span class="hlt">density</span> model to the particle inertia parameter. The scallop features present on the <span class="hlt">ice</span> shapes were thought to generate interstitial flow and horse shoe vortices which enhance the leading edge heat transfer. A set of changes to improve the leading edge heat transfer and the void <span class="hlt">density</span> model were tested. The changes improved the <span class="hlt">ice</span> shape predictions considerably. More work needs to be done to evaluate the performance of these modifications for a wider range of geometries and <span class="hlt">icing</span> conditions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123..864J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123..864J"><span>Ocean-Forced <span class="hlt">Ice</span>-Shelf Thinning in a Synchronously Coupled <span class="hlt">Ice</span>-Ocean Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, James R.; Holland, Paul R.; Goldberg, Dan; Snow, Kate; Arthern, Robert; Campin, Jean-Michel; Heimbach, Patrick; Jenkins, Adrian</p> <p>2018-02-01</p> <p>The first fully synchronous, coupled <span class="hlt">ice</span> shelf-ocean model with a fixed grounding line and imposed upstream <span class="hlt">ice</span> velocity has been developed using the MITgcm (Massachusetts Institute of Technology general circulation model). Unlike previous, asynchronous, approaches to coupled modeling our approach is fully conservative of heat, salt, and <span class="hlt">mass</span>. Synchronous coupling is achieved by continuously updating the <span class="hlt">ice</span>-shelf thickness on the ocean time step. By simulating an idealized, warm-water <span class="hlt">ice</span> shelf we show how raising the pycnocline leads to a reduction in both <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> and back stress, and hence buttressing. Coupled runs show the formation of a western boundary channel in the <span class="hlt">ice</span>-shelf base due to increased melting on the western boundary due to Coriolis enhanced flow. Eastern boundary <span class="hlt">ice</span> thickening is also observed. This is not the case when using a simple depth-dependent parameterized melt, as the <span class="hlt">ice</span> shelf has relatively thinner sides and a thicker central "bulge" for a given <span class="hlt">ice</span>-shelf <span class="hlt">mass</span>. <span class="hlt">Ice</span>-shelf geometry arising from the parameterized melt rate tends to underestimate backstress (and therefore buttressing) for a given <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> due to a thinner <span class="hlt">ice</span> shelf at the boundaries when compared to coupled model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002070','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002070"><span>Assessment of Antarctic <span class="hlt">Ice</span>-Sheet <span class="hlt">Mass</span> Balance Estimates: 1992 - 2009</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Giovinetto, Mario B.</p> <p>2011-01-01</p> <p>Published <span class="hlt">mass</span> balance estimates for the Antarctic <span class="hlt">Ice</span> Sheet (AIS) lie between approximately +50 to -250 Gt/year for 1992 to 2009, which span a range equivalent to 15% of the annual <span class="hlt">mass</span> input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar-altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (+28 and -31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (-40 to -246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. Although recent reports of large and accelerating rates of <span class="hlt">mass</span> loss from GRACE=based studies cite agreement with IOM results, our evaluation does not support that conclusion. We find that the extrapolation used in the published IOM estimates for the 15 % of the periphery for which discharge velocities are not observed gives twice the rate of discharge per unit of associated <span class="hlt">ice</span>-sheet area than the 85% faster-moving parts. Our calculations show that the published extrapolation overestimates the <span class="hlt">ice</span> discharge by 282 Gt/yr compared to our assumption that the slower moving areas have 70% as much discharge per area as the faster moving parts. Also, published data on the time-series of discharge velocities and accumulation/precipitation do not support <span class="hlt">mass</span> output increases or input decreases with time, respectively. Our modified IOM estimate, using the 70% discharge assumption and substituting input from a field-data compilation for input from an atmospheric model over 6% of area, gives a loss of only 13 Gt/year (versus 136 Gt/year) for the period around 2000. Two ERS-based estimates, our modified IOM, and a GRACE-based estimate for observations within 1992 to 2005 lie in a narrowed range of +27 to - 40 Gt/year, which is about 3% of the annual <span class="hlt">mass</span> input and only 0.2 mm/year SLE. Our preferred estimate for 1992-2001 is - 47 Gt</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...845...68P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...845...68P"><span>Dust <span class="hlt">Density</span> Distribution and Imaging Analysis of Different <span class="hlt">Ice</span> Lines in Protoplanetary Disks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pinilla, P.; Pohl, A.; Stammler, S. M.; Birnstiel, T.</p> <p>2017-08-01</p> <p>Recent high angular resolution observations of protoplanetary disks at different wavelengths have revealed several kinds of structures, including multiple bright and dark rings. Embedded planets are the most used explanation for such structures, but there are alternative models capable of shaping the dust in rings as it has been observed. We assume a disk around a Herbig star and investigate the effect that <span class="hlt">ice</span> lines have on the dust evolution, following the growth, fragmentation, and dynamics of multiple dust size particles, covering from 1 μm to 2 m sized objects. We use simplified prescriptions of the fragmentation velocity threshold, which is assumed to change radially at the location of one, two, or three <span class="hlt">ice</span> lines. We assume changes at the radial location of main volatiles, specifically H2O, CO2, and NH3. Radiative transfer calculations are done using the resulting dust <span class="hlt">density</span> distributions in order to compare with current multiwavelength observations. We find that the structures in the dust <span class="hlt">density</span> profiles and radial intensities at different wavelengths strongly depend on the disk viscosity. A clear gap of emission can be formed between <span class="hlt">ice</span> lines and be surrounded by ring-like structures, in particular between the H2O and CO2 (or CO). The gaps are expected to be shallower and narrower at millimeter emission than at near-infrared, opposite to model predictions of particle trapping. In our models, the total gas surface <span class="hlt">density</span> is not expected to show strong variations, in contrast to other gap-forming scenarios such as embedded giant planets or radial variations of the disk viscosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060024016','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060024016"><span><span class="hlt">Mass</span> Changes of the Greenland and Antarctic <span class="hlt">Ice</span> Sheets and Shelves and Contributions to Sea-level Rise: 1992-2002</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Giovinetto, Mario B.; Li, Jun; Cornejo, Helen G.; Beckley, Matthew A.; Brenner, Anita C.; Saba, Jack L.; Yi, Donghui</p> <p>2005-01-01</p> <p>Changes in <span class="hlt">ice</span> <span class="hlt">mass</span> are estimated from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2. For the first time, the dH/dt values are adjusted for changes in surface elevation resulting from temperature-driven variations in the rate of fun compaction. The Greenland <span class="hlt">ice</span> sheet is thinning at the margins (-42 plus or minus 2 Gta(sup -1) below the equilibrium line altitude (ELA)) and growing inland (+53 plus or minus 2 Gt a(sup -1)above the ELA) with a small overall <span class="hlt">mass</span> gain (+11 plus or minus 3 Gt a(sup -1); -0.03 mm a(sup -1) SLE (sea level equivalent)). The <span class="hlt">ice</span> sheet in West Antarctica (WA) is losing <span class="hlt">mass</span> (-47 (dot) 4 GT a(sup -1) and the <span class="hlt">ice</span> sheet in East Antarctica (EA) shows a small <span class="hlt">mass</span> gain (+16 plus or minus 11 Gt a(sup -1) for a combined net change of -31 plus or minus 12 Gt a(sup -1) (+0.08 mm a(sup -1) SLE)). The contribution of the three <span class="hlt">ice</span> sheets to sea level is +0.05 plus or minus 0.03 mm a(sup -1). The Antarctic <span class="hlt">ice</span> shelves show corresponding <span class="hlt">mass</span> changes of -95 (dot) 11 Gt a(sup -1) in WA and +142 plus or minus 10 Gt a(sup -1) in EA. Thinning at the margins of the Greenland <span class="hlt">ice</span> sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate. The marked thinnings in the Pine Island and Thwaites Glacier basins of WA and the Totten Glacier basin in EA are probably <span class="hlt">ice</span>-dynamic responses to long-term climate change and perhaps past removal of their adjacent <span class="hlt">ice</span> shelves. The <span class="hlt">ice</span> growth in the southern Antarctic Peninsula and parts of EA may be due to increasing precipitation during the last century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950025364','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950025364"><span>CO2 (dry <span class="hlt">ice</span>) cleaning system</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barnett, Donald M.</p> <p>1995-01-01</p> <p>Tomco Equipment Company has participated in the dry <span class="hlt">ice</span> (solid carbon dioxide, CO2) cleaning industry for over ten years as a pioneer in the manufacturer of high <span class="hlt">density</span>, dry <span class="hlt">ice</span> cleaning pellet production equipment. For over four years Tomco high <span class="hlt">density</span> pelletizers have been available to the dry <span class="hlt">ice</span> cleaning industry. Approximately one year ago Tomco introduced the DI-250, a new dry <span class="hlt">ice</span> blast unit making Tomco a single source supplier for sublimable media, particle blast, cleaning systems. This new blast unit is an all pneumatic, single discharge hose device. It meters the insertion of 1/8 inch diameter (or smaller), high <span class="hlt">density</span>, dry <span class="hlt">ice</span> pellets into a high pressure, propellant gas stream. The dry <span class="hlt">ice</span> and propellant streams are controlled and mixed from the blast cabinet. From there the mixture is transported to the nozzle where the pellets are accelerated to an appropriate blasting velocity. When directed to impact upon a target area, these dry <span class="hlt">ice</span> pellets have sufficient energy to effectively remove most surface coatings through dry, abrasive contact. The meta-stable, dry <span class="hlt">ice</span> pellets used for CO2 cleaning, while labeled 'high <span class="hlt">density</span>,' are less dense than alternate, abrasive, particle blast media. In addition, after contacting the target surface, they return to their equilibrium condition: a superheated gas state. Most currently used grit blasting media are silicon dioxide based, which possess a sharp tetrahedral molecular structure. Silicon dioxide crystal structures will always produce smaller sharp-edged replicas of the original crystal upon fracture. Larger, softer dry <span class="hlt">ice</span> pellets do not share the same sharp-edged crystalline structures as their non-sublimable counterparts when broken. In fact, upon contact with the target surface, dry <span class="hlt">ice</span> pellets will plastically deform and break apart. As such, dry <span class="hlt">ice</span> cleaning is less harmful to sensitive substrates, workers and the environment than chemical or abrasive cleaning systems. Dry <span class="hlt">ice</span> cleaning system</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.G13B1099B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G13B1099B"><span>Measuring Two Decades of <span class="hlt">Ice</span> <span class="hlt">Mass</span> Loss using GRACE and SLR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonin, J. A.; Chambers, D. P.</p> <p>2016-12-01</p> <p>We use Satellite Laser Ranging (SLR) to extend the time series of <span class="hlt">ice</span> <span class="hlt">mass</span> change back in time to 1994. The SLR series is of far lesser spatial resolution than GRACE, so we apply a constrained inversion technique to better localize the signal. We approximate the likely errors due to SLR's measurement errors combined with the inversion errors from using a low-resolution series, then estimate the interannual <span class="hlt">mass</span> change over Greenland and Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B"><span>Quantifying <span class="hlt">ice</span> cliff contribution to debris-covered glacier <span class="hlt">mass</span> balance from multiple sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brun, Fanny; Wagnon, Patrick; Berthier, Etienne; Kraaijenbrink, Philip; Immerzeel, Walter; Shea, Joseph; Vincent, Christian</p> <p>2017-04-01</p> <p><span class="hlt">Ice</span> cliffs on debris-covered glaciers have been recognized as a hot spot for glacier melt. <span class="hlt">Ice</span> cliffs are steep (even sometimes overhanging) and fast evolving surface features, which make them challenging to monitor. We surveyed the topography of Changri Nup Glacier (Nepalese Himalayas, Everest region) in November 2015 and 2016 using multiple sensors: terrestrial photogrammetry, Unmanned Aerial Vehicle (UAV) photogrammetry, Pléiades stereo images and ASTER stereo images. We derived 3D point clouds and digital elevation models (DEMs) following a Structure-from-Motion (SfM) workflow for the first two sets of data to monitor surface elevation changes and calculate the associated volume loss. We derived only DEMs for the two last data sets. The derived DEMs had resolutions ranging from < 5 cm to 30 m. The derived point clouds and DEMs are used to quantify the <span class="hlt">ice</span> melt of the cliffs at different scales. The very high resolution SfM point clouds, together with the surface velocity field, will be used to calculate the volume losses of 14 individual cliffs, depending on their size, aspect or the presence of supra glacial lake. Then we will extend this analysis to the whole glacier to quantify the contribution of <span class="hlt">ice</span> cliff melt to the overall glacier <span class="hlt">mass</span> balance, calculated with the UAV and Pléiades DEMs. This research will provide important tools to evaluate the role of <span class="hlt">ice</span> cliffs in regional <span class="hlt">mass</span> loss.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A22E..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A22E..01H"><span>On The Importance of Connecting Laboratory Measurements of <span class="hlt">Ice</span> Crystal Growth with Model Parameterizations: Predicting <span class="hlt">Ice</span> Particle Properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harrington, J. Y.</p> <p>2017-12-01</p> <p>Parameterizing the growth of <span class="hlt">ice</span> particles in numerical models is at an interesting cross-roads. Most parameterizations developed in the past, including some that I have developed, parse model <span class="hlt">ice</span> into numerous categories based primarily on the growth mode of the particle. Models routinely possess smaller <span class="hlt">ice</span>, snow crystals, aggregates, graupel, and hail. The snow and <span class="hlt">ice</span> categories in some models are further split into subcategories to account for the various shapes of <span class="hlt">ice</span>. There has been a relatively recent shift towards a new class of microphysical models that predict the properties of <span class="hlt">ice</span> particles instead of using multiple categories and subcategories. Particle property models predict the physical characteristics of <span class="hlt">ice</span>, such as aspect ratio, maximum dimension, effective <span class="hlt">density</span>, rime <span class="hlt">density</span>, effective area, and so forth. These models are attractive in the sense that particle characteristics evolve naturally in time and space without the need for numerous (and somewhat artificial) transitions among pre-defined classes. However, particle property models often require fundamental parameters that are typically derived from laboratory measurements. For instance, the evolution of particle shape during vapor depositional growth requires knowledge of the growth efficiencies for the various axis of the crystals, which in turn depends on surface parameters that can only be determined in the laboratory. The evolution of particle shapes and <span class="hlt">density</span> during riming, aggregation, and melting require data on the redistribution of <span class="hlt">mass</span> across a crystals axis as that crystal collects water drops, <span class="hlt">ice</span> crystals, or melts. Predicting the evolution of particle properties based on laboratory-determined parameters has a substantial influence on the evolution of some cloud systems. Radiatively-driven cirrus clouds show a broader range of competition between heterogeneous nucleation and homogeneous freezing when <span class="hlt">ice</span> crystal properties are predicted. Even strongly convective squall</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110006429','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110006429"><span>Changes in the <span class="hlt">Mass</span> Balance of the Greenland <span class="hlt">Ice</span> Sheet in a Warming Climate During 2003-2009</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, H. Jay; Luthcke, Scott</p> <p>2010-01-01</p> <p><span class="hlt">Mass</span> changes of the Greenland <span class="hlt">ice</span> sheet (GIS) derived from ICESat and GRACE data both show that the net <span class="hlt">mass</span> loss from GIS during 2003-2009 is about 175 Gt/year, which contributes 0.5mm/yr global sea-level rise. The rate of <span class="hlt">mass</span> loss has increased significantly since the 1990's when the GIS was close to <span class="hlt">mass</span> balance. Even though the GIS was close to <span class="hlt">mass</span> balance during the 1990's, it was already showing characteristics of responding to8 warmer climate, specifically thinning at the margins and thickening inland at higher elevations. During 2003-2009, increased <span class="hlt">ice</span> thinning due to increases in melting and acceleration of outlet glaciers began to strongly exceed the inland thickening from increases in accumulation. Over the entire GIS, the <span class="hlt">mass</span> loss between the two periods, from increased melting and <span class="hlt">ice</span> dynamics, increased by about 190 Gt/year while the <span class="hlt">mass</span> gain, from increased precipitation and accumulation, increased by only about 15Gt/year. These <span class="hlt">ice</span> changes occurred during a time when the temperature on GIS changed at rate of about 2K/decade. The distribution of elevation and <span class="hlt">mass</span> changes derived from ICESat have high spatial resolution showing details over outlet glaciers, by drainage systems, and by elevation. However, information on the seasonal cycle of changes from ICESat data is limited, because the ICESat lasers were only operated during two to three campaigns per year of about 35 days duration each. In contrast, the temporal resolution of GRACE data, provided by the continuous data collection, is much better showing details of the seasonal cycle and the inter-annual variability. The differing sensitivity of the ICESat altimetry and the GRACE gravity methods to motion of the underlying bedrock from glacial isostatic adjustment (GIA) is used to evaluate the GIA corrections provided by models. The two data types are also combined to make estimates of the partitioning of the <span class="hlt">mass</span> gains and losses among accumulation, melting, and <span class="hlt">ice</span> discharge from outlet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA617621','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA617621"><span>Wave-<span class="hlt">Ice</span> and Air-<span class="hlt">Ice</span>-Ocean Interaction During the Chukchi Sea <span class="hlt">Ice</span> Edge Advance</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-09-30</p> <p>During cruise CU-B UAF UW Airborne expendable <span class="hlt">Ice</span> Buoy (AXIB) Ahead, at and inside <span class="hlt">ice</span> edge Surface meteorology T, SLP ~1 year CU-B UW...Balance (IMB) buoys Inside <span class="hlt">ice</span> edge w/ >50cm thickness <span class="hlt">Ice</span> <span class="hlt">mass</span> balance T in snow-<span class="hlt">ice</span>-ocean, T, SLP at surface ~1 year WHOI CRREL (SeaState DRI</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2621C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2621C"><span>Retrieval of <span class="hlt">ice</span> crystals' <span class="hlt">mass</span> from <span class="hlt">ice</span> water content and particle distribution measurements: a numerical optimization approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter</p> <p>2016-04-01</p> <p>A new method to retrieve cloud water content from in-situ measured 2D particle images from optical array probes (OAP) is presented. With the overall objective to build a statistical model of crystals' <span class="hlt">mass</span> as a function of their size, environmental temperature and crystal microphysical history, this study presents the methodology to retrieve the <span class="hlt">mass</span> of crystals sorted by size from 2D images using a numerical optimization approach. The methodology is validated using two datasets of in-situ measurements gathered during two airborne field campaigns held in Darwin, Australia (2014), and Cayenne, France (2015), in the frame of the High Altitude <span class="hlt">Ice</span> Crystals (HAIC) / High <span class="hlt">Ice</span> Water Content (HIWC) projects. During these campaigns, a Falcon F-20 research aircraft equipped with state-of-the art microphysical instrumentation sampled numerous mesoscale convective systems (MCS) in order to study dynamical and microphysical properties and processes of high <span class="hlt">ice</span> water content areas. Experimentally, an isokinetic evaporator probe, referred to as IKP-2, provides a reference measurement of the total water content (TWC) which equals <span class="hlt">ice</span> water content, (IWC) when (supercooled) liquid water is absent. Two optical array probes, namely 2D-S and PIP, produce 2D images of individual crystals ranging from 50 μm to 12840 μm from which particle size distributions (PSD) are derived. Mathematically, the problem is formulated as an inverse problem in which the crystals' <span class="hlt">mass</span> is assumed constant over a size class and is computed for each size class from IWC and PSD data: PSD.m = IW C This problem is solved using numerical optimization technique in which an objective function is minimized. The objective function is defined as follows: 2 J(m)=∥P SD.m - IW C ∥ + λ.R (m) where the regularization parameter λ and the regularization function R(m) are tuned based on data characteristics. The method is implemented in two steps. First, the method is developed on synthetic crystal populations in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940017861','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940017861"><span>Normalized vertical <span class="hlt">ice</span> <span class="hlt">mass</span> flux profiles from vertically pointing 8-mm-wavelength Doppler radar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Orr, Brad W.; Kropfli, Robert A.</p> <p>1993-01-01</p> <p>During the FIRE 2 (First International Satellite Cloud Climatology Project Regional Experiment) project, NOAA's Wave Propagation Laboratory (WPL) operated its 8-mm wavelength Doppler radar extensively in the vertically pointing mode. This allowed for the calculation of a number of important cirrus cloud parameters, including cloud boundary statistics, cloud particle characteristic sizes and concentrations, and <span class="hlt">ice</span> <span class="hlt">mass</span> content (imc). The flux of imc, or, alternatively, <span class="hlt">ice</span> <span class="hlt">mass</span> flux (imf), is also an important parameter of a cirrus cloud system. <span class="hlt">Ice</span> <span class="hlt">mass</span> flux is important in the vertical redistribution of water substance and thus, in part, determines the cloud evolution. It is important for the development of cloud parameterizations to be able to define the essential physical characteristics of large populations of clouds in the simplest possible way. One method would be to normalize profiles of observed cloud properties, such as those mentioned above, in ways similar to those used in the convective boundary layer. The height then scales from 0.0 at cloud base to 1.0 at cloud top, and the measured cloud parameter scales by its maximum value so that all normalized profiles have 1.0 as their maximum value. The goal is that there will be a 'universal' shape to profiles of the normalized data. This idea was applied to estimates of imf calculated from data obtained by the WPL cloud radar during FIRE II. Other quantities such as median particle diameter, concentration, and <span class="hlt">ice</span> <span class="hlt">mass</span> content can also be estimated with this radar, and we expect to also examine normalized profiles of these quantities in time for the 1993 FIRE II meeting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663264-dust-density-distribution-imaging-analysis-different-ice-lines-protoplanetary-disks','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663264-dust-density-distribution-imaging-analysis-different-ice-lines-protoplanetary-disks"><span>Dust <span class="hlt">Density</span> Distribution and Imaging Analysis of Different <span class="hlt">Ice</span> Lines in Protoplanetary Disks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Pinilla, P.; Pohl, A.; Stammler, S. M.</p> <p></p> <p>Recent high angular resolution observations of protoplanetary disks at different wavelengths have revealed several kinds of structures, including multiple bright and dark rings. Embedded planets are the most used explanation for such structures, but there are alternative models capable of shaping the dust in rings as it has been observed. We assume a disk around a Herbig star and investigate the effect that <span class="hlt">ice</span> lines have on the dust evolution, following the growth, fragmentation, and dynamics of multiple dust size particles, covering from 1 μ m to 2 m sized objects. We use simplified prescriptions of the fragmentation velocity threshold,more » which is assumed to change radially at the location of one, two, or three <span class="hlt">ice</span> lines. We assume changes at the radial location of main volatiles, specifically H{sub 2}O, CO{sub 2}, and NH{sub 3}. Radiative transfer calculations are done using the resulting dust <span class="hlt">density</span> distributions in order to compare with current multiwavelength observations. We find that the structures in the dust <span class="hlt">density</span> profiles and radial intensities at different wavelengths strongly depend on the disk viscosity. A clear gap of emission can be formed between <span class="hlt">ice</span> lines and be surrounded by ring-like structures, in particular between the H{sub 2}O and CO{sub 2} (or CO). The gaps are expected to be shallower and narrower at millimeter emission than at near-infrared, opposite to model predictions of particle trapping. In our models, the total gas surface <span class="hlt">density</span> is not expected to show strong variations, in contrast to other gap-forming scenarios such as embedded giant planets or radial variations of the disk viscosity.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C23B0613H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C23B0613H"><span>Polar <span class="hlt">Ice</span> Caps: a Canary for the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Honsaker, W.; Lowell, T. V.; Sagredo, E.; Kelly, M. A.; Hall, B. L.</p> <p>2010-12-01</p> <p><span class="hlt">Ice</span> caps are glacier <span class="hlt">masses</span> that are highly sensitive to climate change. Because of their hypsometry they can have a binary state. When relatively slight changes in the equilibrium line altitude (ELA) either intersect or rise above the land the <span class="hlt">ice</span> can become established or disappear. Thus these upland <span class="hlt">ice</span> <span class="hlt">masses</span> have a fast response time. Here we consider a way to extract the ELA signal from independent <span class="hlt">ice</span> caps adjacent to the Greenland <span class="hlt">Ice</span> Sheet margin. It may be that these <span class="hlt">ice</span> caps are sensitive trackers of climate change that also impact the <span class="hlt">ice</span> sheet margin. One example is the Istorvet <span class="hlt">Ice</span> Cap located in Liverpool Land, East Greenland (70.881°N, 22.156°W). The <span class="hlt">ice</span> cap topography and the underlying bedrock surface dips to the north, with peak elevation of the current <span class="hlt">ice</span> ranging in elevation from 1050 to 745 m.a.s.l. On the eastern side of the <span class="hlt">ice</span> <span class="hlt">mass</span> the outlet glaciers extending down to sea level. The western margin has several small lobes in topographic depressions, with the margin reaching down to 300 m.a.s.l. Topographic highs separate the <span class="hlt">ice</span> cap into at least 5 main catchments, each having a pair of outlet lobes toward either side of the <span class="hlt">ice</span> cap. Because of the regional bedrock slope each catchment has its own elevation range. Therefore, as the ELA changes it is possible for some catchments of the <span class="hlt">ice</span> cap to experience positive <span class="hlt">mass</span> balance while others have a negative balance. Based on weather observations we estimate the present day ELA to be ~1000 m.a.s.l, meaning <span class="hlt">mass</span> balance is negative for the majority of the <span class="hlt">ice</span> cap. By tracking glacier presence/absence in these different catchments, we can reconstruct small changes in the ELA. Another example is the High <span class="hlt">Ice</span> Cap (informal name) in Milne Land (70.903°N, 25.626°W, 1080 m), East Greenland. Here at least 4 unconformities in <span class="hlt">ice</span> layers found near the southern margin of the <span class="hlt">ice</span> cap record changing intervals of accumulation and ablation. Therefore, this location may also be sensitive to slight</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JChPh.143c4702B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JChPh.143c4702B"><span>Latent heat induced rotation limited aggregation in 2D <span class="hlt">ice</span> nanocrystals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bampoulis, Pantelis; Siekman, Martin H.; Kooij, E. Stefan; Lohse, Detlef; Zandvliet, Harold J. W.; Poelsema, Bene</p> <p>2015-07-01</p> <p>The basic science responsible for the fascinating shapes of <span class="hlt">ice</span> crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D <span class="hlt">ice</span>. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D <span class="hlt">ice</span> nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low <span class="hlt">mass</span> <span class="hlt">density</span> mother phase, in contrast to the actual currently present high <span class="hlt">mass</span> <span class="hlt">density</span> mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (<span class="hlt">ice</span>) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D <span class="hlt">ice</span> nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D <span class="hlt">ice</span> nanocrystals to local temperature dependent rotation limited aggregation. The <span class="hlt">ice</span> growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (<span class="hlt">ice</span>) flakes and we consider our findings crucial for solving the "perennial" snow (<span class="hlt">ice</span>) flake enigma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9829W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9829W"><span><span class="hlt">Mass</span> loss of the Greenland peripheral glaciers and <span class="hlt">ice</span> caps from satellite altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wouters, Bert; Noël, Brice; Moholdt, Geir; Ligtenberg, Stefan; van den Broeke, Michiel</p> <p>2017-04-01</p> <p>At its rapidly warming margins, the Greenland <span class="hlt">Ice</span> Sheet is surrounded by (semi-)detached glaciers and <span class="hlt">ice</span> caps (GIC). Although they cover only roughly 5% of the total glaciated area in the region, they are estimated to account for 15-20% of the total sea level rise contribution of Greenland. The spatial and temporal evolution of the <span class="hlt">mass</span> changes of the peripheral GICs, however, remains poorly constrained. In this presentation, we use satellite altimetry from ICESat and Cryosat-2 combined with a high-resolution regional climate model to derive a 14 year time series (2003-2016) of regional elevation and <span class="hlt">mass</span> changes. The total <span class="hlt">mass</span> loss has been relatively constant during this period, but regionally, the GICs show marked temporal variations. Whereas thinning was concentrated along the eastern margin during 2003-2009, western GICs became the prime sea level rise contributors in recent years. <span class="hlt">Mass</span> loss in the northern region has been steadily increasing throughout the record, due to a strong atmospheric warning and a deterioration of the capacity of the firn layer to buffer the resulting melt water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11884754','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11884754"><span>Antarctic krill under sea <span class="hlt">ice</span>: elevated abundance in a narrow band just south of <span class="hlt">ice</span> edge.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brierley, Andrew S; Fernandes, Paul G; Brandon, Mark A; Armstrong, Frederick; Millard, Nicholas W; McPhail, Steven D; Stevenson, Peter; Pebody, Miles; Perrett, James; Squires, Mark; Bone, Douglas G; Griffiths, Gwyn</p> <p>2002-03-08</p> <p>We surveyed Antarctic krill (Euphausia superba) under sea <span class="hlt">ice</span> using the autonomous underwater vehicle Autosub-2. Krill were concentrated within a band under <span class="hlt">ice</span> between 1 and 13 kilometers south of the <span class="hlt">ice</span> edge. Within this band, krill <span class="hlt">densities</span> were fivefold greater than that of open water. The under-<span class="hlt">ice</span> environment has long been considered an important habitat for krill, but sampling difficulties have previously prevented direct observations under <span class="hlt">ice</span> over the scale necessary for robust krill <span class="hlt">density</span> estimation. Autosub-2 enabled us to make continuous high-resolution measurements of krill <span class="hlt">density</span> under <span class="hlt">ice</span> reaching 27 kilometers beyond the <span class="hlt">ice</span> edge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C53B1037M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C53B1037M"><span>Continuous Estimates of Surface <span class="hlt">Density</span> and Annual Snow Accumulation with Multi-Channel Snow/Firn Penetrating Radar in the Percolation Zone, Western Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meehan, T.; Marshall, H. P.; Bradford, J.; Hawley, R. L.; Osterberg, E. C.; McCarthy, F.; Lewis, G.; Graeter, K.</p> <p>2017-12-01</p> <p>A priority of <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> balance (SMB) prediction is ascertaining the surface <span class="hlt">density</span> and annual snow accumulation. These forcing data can be supplied into firn compaction models and used to tune Regional Climate Models (RCM). RCMs do not accurately capture subtle changes in the snow accumulation gradient. Additionally, leading RCMs disagree among each other and with accumulation studies in regions of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) over large distances and temporal scales. RCMs tend to yield inconsistencies over GrIS because of sparse and outdated validation data in the reanalysis pool. Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) implemented multi-channel 500 MHz Radar in multi-offset configuration throughout two traverse campaigns totaling greater than 3500 km along the western percolation zone of GrIS. The multi-channel radar has the capability of continuously estimating snow depth, average <span class="hlt">density</span>, and annual snow accumulation, expressed at 95% confidence (+-) 0.15 m, (+-) 17 kgm-3, (+-) 0.04 m w.e. respectively, by examination of the primary reflection return from the previous year's summer surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31E..01Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31E..01Z"><span>Transient <span class="hlt">ice</span> <span class="hlt">mass</span> variations over Greenland detected by the combination of GPS and GRACE data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, B.; Liu, L.; Khan, S. A.; van Dam, T. M.; Zhang, E.</p> <p>2017-12-01</p> <p>Over the past decade, the Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been undergoing significant warming and <span class="hlt">ice</span> <span class="hlt">mass</span> loss. Such <span class="hlt">mass</span> loss was not always a steady process but had substantial temporal and spatial variabilities. Here we apply multi-channel singular spectral analysis to crustal deformation time series measured at about 50 Global Positioning System (GPS) stations mounted on bedrock around the Greenland coast and <span class="hlt">mass</span> changes inferred from Gravity Recovery and Climate Experiment (GRACE) to detect transient changes in <span class="hlt">ice</span> <span class="hlt">mass</span> balance over the GrIS. We detect two transient anomalies: one is a negative melting anomaly (Anomaly 1) that peaked around 2010; the other is a positive melting anomaly (Anomaly 2) that peaked between 2012 and 2013. The GRACE data show that both anomalies caused significant <span class="hlt">mass</span> changes south of 74°N but negligible changes north of 74°N. Both anomalies caused the maximum <span class="hlt">mass</span> change in southeast GrIS, followed by in west GrIS near Jakobshavn. Our results also show that the <span class="hlt">mass</span> change caused by Anomaly 1 first reached the maximum in late 2009 in the southeast GrIS and then migrated to west GrIS. However, in Anomaly 2, the southeast GrIS was the last place that reached the maximum <span class="hlt">mass</span> change in early 2013 and the west GrIS near Jakobshavn was the second latest place that reached the maximum <span class="hlt">mass</span> change. Most of the GPS data show similar spatiotemporal patterns as those obtained from the GRACE data. However, some GPS time series show discrepancies in either space or time, because of data gaps and different sensitivities of <span class="hlt">mass</span> loading change. Namely, loading deformation measured by GPS can be significantly affected by local dynamical <span class="hlt">mass</span> changes, which, yet, has little impact on GRACE observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22525155-distinguishing-neutrino-mass-hierarchies-using-dark-matter-annihilation-signals-icecube','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22525155-distinguishing-neutrino-mass-hierarchies-using-dark-matter-annihilation-signals-icecube"><span>Distinguishing neutrino <span class="hlt">mass</span> hierarchies using dark matter annihilation signals at <span class="hlt">Ice</span>Cube</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Allahverdi, Rouzbeh; Knockel, Bradley; Dutta, Bhaskar</p> <p>2015-12-01</p> <p>We explore the possibility of distinguishing neutrino <span class="hlt">mass</span> hierarchies through the neutrino signal from dark matter annihilation at neutrino telescopes. We consider a simple extension of the standard model where the neutrino <span class="hlt">masses</span> and mixing angles are obtained via the type-II seesaw mechanism as an explicit example. We show that future extensions of <span class="hlt">Ice</span>Cube neutrino telescope may detect the neutrino signal from DM annihilation at the Galactic Center and inside the Sun, and differentiate between the normal and inverted <span class="hlt">mass</span> hierarchies, in this model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28361871','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28361871"><span>A tipping point in refreezing accelerates <span class="hlt">mass</span> loss of Greenland's glaciers and <span class="hlt">ice</span> caps.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Noël, B; van de Berg, W J; Lhermitte, S; Wouters, B; Machguth, H; Howat, I; Citterio, M; Moholdt, G; Lenaerts, J T M; van den Broeke, M R</p> <p>2017-03-31</p> <p>Melting of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its peripheral glaciers and <span class="hlt">ice</span> caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS <span class="hlt">mass</span> loss are well studied, the spatial and temporal evolution of GICs <span class="hlt">mass</span> loss and the acting processes have remained unclear. Here we use a novel, 1 km surface <span class="hlt">mass</span> balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs <span class="hlt">mass</span> balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 <span class="hlt">mass</span> loss to 36±16 Gt -1 , or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5380968','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5380968"><span>A tipping point in refreezing accelerates <span class="hlt">mass</span> loss of Greenland's glaciers and <span class="hlt">ice</span> caps</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Noël, B.; van de Berg, W. J; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.</p> <p>2017-01-01</p> <p>Melting of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its peripheral glaciers and <span class="hlt">ice</span> caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS <span class="hlt">mass</span> loss are well studied, the spatial and temporal evolution of GICs <span class="hlt">mass</span> loss and the acting processes have remained unclear. Here we use a novel, 1 km surface <span class="hlt">mass</span> balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs <span class="hlt">mass</span> balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 <span class="hlt">mass</span> loss to 36±16 Gt−1, or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming. PMID:28361871</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...814730N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...814730N"><span>A tipping point in refreezing accelerates <span class="hlt">mass</span> loss of Greenland's glaciers and <span class="hlt">ice</span> caps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, B.; van de Berg, W. J.; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.</p> <p>2017-03-01</p> <p>Melting of the Greenland <span class="hlt">ice</span> sheet (GrIS) and its peripheral glaciers and <span class="hlt">ice</span> caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS <span class="hlt">mass</span> loss are well studied, the spatial and temporal evolution of GICs <span class="hlt">mass</span> loss and the acting processes have remained unclear. Here we use a novel, 1 km surface <span class="hlt">mass</span> balance product, evaluated against in situ and remote sensing data, to identify 1997 (+/-5 years) as a tipping point for GICs <span class="hlt">mass</span> balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 <span class="hlt">mass</span> loss to 36+/-16 Gt-1, or ~14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23660938','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23660938"><span>Ultra-slow dynamics in low <span class="hlt">density</span> amorphous <span class="hlt">ice</span> revealed by deuteron NMR: indication of a glass transition.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Löw, Florian; Amann-Winkel, Katrin; Loerting, Thomas; Fujara, Franz; Geil, Burkhard</p> <p>2013-06-21</p> <p>The postulated glass-liquid transition of low <span class="hlt">density</span> amorphous <span class="hlt">ice</span> (LDA) is investigated with deuteron NMR stimulated echo experiments. Such experiments give access to ultra-slow reorientations of water molecules on time scales expected for structural relaxation of glass formers close to the glass-liquid transition temperature. An involved data analysis is necessary to account for signal contributions originating from a gradual crystallization to cubic <span class="hlt">ice</span>. Even if some ambiguities remain, our findings support the view that pressure amorphized LDA <span class="hlt">ices</span> are of glassy nature and undergo a glass-liquid transition before crystallization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7457N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7457N"><span>Quantifying the <span class="hlt">mass</span> loss of peripheral Greenland glaciers and <span class="hlt">ice</span> caps (1958-2014).</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; van den Broeke, Michiel</p> <p>2016-04-01</p> <p>Since the 2000s, <span class="hlt">mass</span> loss from Greenland peripheral glaciers and <span class="hlt">ice</span> caps (GICs) has accelerated, becoming an important contributor to sea level rise. Under continued warming throughout the 21st century, GICs might yield up to 7.5 to 11 mm sea level rise, with increasing dominance of surface runoff at the expense of <span class="hlt">ice</span> discharge. However, despite multiple observation campaigns, little remains known about the contribution of GICs to total Greenland <span class="hlt">mass</span> loss. Furthermore, the relatively coarse resolutions in regional climate models, i.e. 5 km to 20 km, fail to represent the small scale patterns of surface <span class="hlt">mass</span> balance (SMB) components over these topographically complex regions including also narrow valley glaciers. Here, we present a novel approach to quantify the contribution of GICs to surface melt and runoff, based on an elevation dependent downscaling method. GICs daily SMB components at 1 km resolution are obtained by statistically downscaling the outputs of RACMO2.3 at 11 km resolution to a down-sampled version of the GIMP DEM for the period 1958-2014. This method has recently been successfully validated over the Greenland <span class="hlt">ice</span> sheet and is now applied to GICs. In this study, we first evaluate the 1 km daily downscaled GICs SMB against a newly available and comprehensive dataset of ablation stake measurements. Then, we investigate present-day trends of meltwater production and SMB for different regions and estimate GICs contribution to total Greenland <span class="hlt">mass</span> loss. These data are considered valuable for model evaluation and prediction of future sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26887494','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26887494"><span><span class="hlt">Ice</span> stream activity scaled to <span class="hlt">ice</span> sheet volume during Laurentide <span class="hlt">Ice</span> Sheet deglaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stokes, C R; Margold, M; Clark, C D; Tarasov, L</p> <p>2016-02-18</p> <p>The contribution of the Greenland and West Antarctic <span class="hlt">ice</span> sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and <span class="hlt">ice</span> streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major <span class="hlt">ice</span> sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response. A major problem is that observations used to initialize and calibrate models typically span only a few decades, and, at the <span class="hlt">ice</span>-sheet scale, it is unclear how the entire drainage network of <span class="hlt">ice</span> streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of <span class="hlt">ice</span> sheets to sea-level rise. A key question is whether <span class="hlt">ice</span> streams might increase and sustain rates of <span class="hlt">mass</span> loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 <span class="hlt">ice</span> streams that operated at various times during deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet (from about 22,000 to 7,000 years ago) and show that as they activated and deactivated in different locations, their overall number decreased, they occupied a progressively smaller percentage of the <span class="hlt">ice</span> sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced <span class="hlt">ice</span> stream activity, but--at the <span class="hlt">ice</span>-sheet scale--their drainage network adjusted and was linked to changes in <span class="hlt">ice</span> sheet volume. It is unclear whether these findings can be directly translated to modern <span class="hlt">ice</span> sheets. However, contrary to the view that sees <span class="hlt">ice</span> streams as unstable entities that can accelerate <span class="hlt">ice</span>-sheet deglaciation, we conclude that <span class="hlt">ice</span> streams exerted progressively less influence on <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance during the retreat of the Laurentide <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Sci...358..781M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Sci...358..781M"><span>Cordilleran <span class="hlt">Ice</span> Sheet <span class="hlt">mass</span> loss preceded climate reversals near the Pleistocene Termination</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menounos, B.; Goehring, B. M.; Osborn, G.; Margold, M.; Ward, B.; Bond, J.; Clarke, G. K. C.; Clague, J. J.; Lakeman, T.; Koch, J.; Caffee, M. W.; Gosse, J.; Stroeven, A. P.; Seguinot, J.; Heyman, J.</p> <p>2017-11-01</p> <p>The Cordilleran <span class="hlt">Ice</span> Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the <span class="hlt">ice</span> sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were <span class="hlt">ice</span> free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the <span class="hlt">mass</span> of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000088622','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000088622"><span>Airborne Laser Altimetry Mapping of the Greenland <span class="hlt">Ice</span> Sheet: Application to <span class="hlt">Mass</span> Balance Assessment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Wright, W.; Yungel, J.</p> <p>2000-01-01</p> <p>In 1998 and '99, the Arctic <span class="hlt">Ice</span> Mapping (AIM) program completed resurveys of lines occupied 5 years earlier revealing elevation changes of the Greenland <span class="hlt">ice</span> sheet and identifying areas of significant thinning, thickening and balance. In planning these surveys, consideration had to be given to the spatial constraints associated with aircraft operation, the spatial nature of <span class="hlt">ice</span> sheet behavior, and limited resources, as well as temporal issues, such as seasonal and interannual variability in the context of measurement accuracy. This paper examines the extent to which the sampling and survey strategy is valid for drawing conclusions on the current state of balance of the Greenland <span class="hlt">ice</span> sheet. The surveys covered the entire <span class="hlt">ice</span> sheet with an average distance of 21.4 km between each location on the <span class="hlt">ice</span> sheet and the nearest flight line. For most of the <span class="hlt">ice</span> sheet, the elevation changes show relatively little spatial variability, and their magnitudes are significantly smaller than the observed elevation change signal. As a result, we conclude that the <span class="hlt">density</span> of the sampling and the accuracy of the measurements are sufficient to draw meaningful conclusions on the state of balance of the entire <span class="hlt">ice</span> sheet over the five-year survey period. Outlet glaciers, however, show far more spatial and temporal variability, and each of the major ones is likely to require individual surveys in order to determine its balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMED33A0619H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMED33A0619H"><span><span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby!</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamilton, C.</p> <p>2008-12-01</p> <p>The Center for Remote Sensing of <span class="hlt">Ice</span> Sheets (CReSIS) has developed an outreach program based on hands-on activities called "<span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby". These lessons are designed to teach the science principles of displacement, forces of motion, <span class="hlt">density</span>, and states of matter. These properties are easily taught through the interesting topics of glaciers, icebergs, and sea level rise in K-8 classrooms. The activities are fun, engaging, and simple enough to be used at science fairs and family science nights. Students who have participated in "<span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby" have successfully taught these to adults and students at informal events. The lessons are based on education standards which are available on our website www.cresis.ku.edu. This presentation will provide information on the activities, survey results from teachers who have used the material, and other suggested material that can be used before and after the activities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26203037','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26203037"><span>Latent heat induced rotation limited aggregation in 2D <span class="hlt">ice</span> nanocrystals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bampoulis, Pantelis; Siekman, Martin H; Kooij, E Stefan; Lohse, Detlef; Zandvliet, Harold J W; Poelsema, Bene</p> <p>2015-07-21</p> <p>The basic science responsible for the fascinating shapes of <span class="hlt">ice</span> crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D <span class="hlt">ice</span>. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D <span class="hlt">ice</span> nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low <span class="hlt">mass</span> <span class="hlt">density</span> mother phase, in contrast to the actual currently present high <span class="hlt">mass</span> <span class="hlt">density</span> mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (<span class="hlt">ice</span>) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D <span class="hlt">ice</span> nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D <span class="hlt">ice</span> nanocrystals to local temperature dependent rotation limited aggregation. The <span class="hlt">ice</span> growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (<span class="hlt">ice</span>) flakes and we consider our findings crucial for solving the "perennial" snow (<span class="hlt">ice</span>) flake enigma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15789601','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15789601"><span><span class="hlt">Mass</span> <span class="hlt">density</span> images from the diffraction enhanced imaging technique.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hasnah, M O; Parham, C; Pisano, E D; Zhong, Z; Oltulu, O; Chapman, D</p> <p>2005-02-01</p> <p>Conventional x-ray radiography measures the projected x-ray attenuation of an object. It requires attenuation differences to obtain contrast of embedded features. In general, the best absorption contrast is obtained at x-ray energies where the absorption is high, meaning a high absorbed dose. Diffraction-enhanced imaging (DEI) derives contrast from absorption, refraction, and extinction. The refraction angle image of DEI visualizes the spatial gradient of the projected electron <span class="hlt">density</span> of the object. The projected electron <span class="hlt">density</span> often correlates well with the projected <span class="hlt">mass</span> <span class="hlt">density</span> and projected absorption in soft-tissue imaging, yet the <span class="hlt">mass</span> <span class="hlt">density</span> is not an "energy"-dependent property of the object, as is the case of absorption. This simple difference can lead to imaging with less x-ray exposure or dose. In addition, the <span class="hlt">mass</span> <span class="hlt">density</span> image can be directly compared (i.e., a signal-to-noise comparison) with conventional radiography. We present the method of obtaining the <span class="hlt">mass</span> <span class="hlt">density</span> image, the results of experiments in which comparisons are made with radiography, and an application of the method to breast cancer imaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33D1236L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33D1236L"><span>Geodetic <span class="hlt">mass</span> balance measurements on debris and clean-<span class="hlt">ice</span> tropical glaciers in Ecuador</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>La Frenierre, J.; Decker, C. R.; Jordan, E.; Wigmore, O.; Hodge, B. E.; Niederriter, C.; Michels, A.</p> <p>2017-12-01</p> <p>Glaciers are recognized as highly sensitive indicators of climate change in high altitude, low latitude environments. In the tropical Andes, various analyses of glacier surface area change have helped illuminate the manifestation of climate change in this region, however, information about actual glacier <span class="hlt">mass</span> balance behavior is much more limited given the relatively small glaciers, difficult access, poor weather, and/or limited local resources common here. Several new technologies, including aerial and terrestrial LIDAR and structure-from-motion photogrammetry using small unmanned aerial vehicles (UAVs), make <span class="hlt">mass</span> balance measurements using geodetic approaches increasingly feasible in remote mountain locations, which can both further our understanding of changing climatic conditions, and improve our ability to evaluate the downstream hydrologic impacts of <span class="hlt">ice</span> loss. At Volcán Chimborazo, Ecuador, these new technologies, combined with a unique, 5-meter resolution digital elevation model derived from 1997 aerial imagery, make possible an analysis of the magnitude and spatial patterns of <span class="hlt">mass</span> balance behavior over the past two decades. Here, we evaluate <span class="hlt">ice</span> loss between 1997 and 2017 at the tongues of two adjacent glaciers, one debris-covered and detached from its accumulation area (Reschreiter Glacier), and one debris-free and intact (Hans Meyer Glacier). Additionally, we incorporate data from 2012 and 2013 terrestrial LIDAR surveys to evaluate the behavior of the Reschreiter at a finer temporal resolution. We find that on the Hans Meyer, the mean surface deflation rate since 1997 at the present-day tongue has been nearly 3 m yr-1, while on the lower-elevation Reschreiter, the mean deflation rate has been approximately 1 m yr-1. However, the processes by which debris-covered <span class="hlt">ice</span> becomes exposed results in highly heterogeneous patterns of <span class="hlt">ice</span> loss, with some areas experiencing surface deflation rates approaching 15 m yr-1 when energy absorption is unimpeded.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15268606','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15268606"><span>Investigation of vapor-deposited amorphous <span class="hlt">ice</span> and irradiated <span class="hlt">ice</span> by molecular dynamics simulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guillot, Bertrand; Guissani, Yves</p> <p>2004-03-01</p> <p>With the purpose of clarifying a number of points raised in the experimental literature, we investigate by molecular dynamics simulation the thermodynamics, the structure and the vibrational properties of vapor-deposited amorphous <span class="hlt">ice</span> (ASW) as well as the phase transformations experienced by crystalline and vitreous <span class="hlt">ice</span> under ion bombardment. Concerning ASW, we have shown that by changing the conditions of the deposition process, it is possible to form either a nonmicroporous amorphous deposit whose <span class="hlt">density</span> (approximately 1.0 g/cm3) is essentially invariant with the temperature of deposition, or a microporous sample whose <span class="hlt">density</span> varies drastically upon temperature annealing. We find that ASW is energetically different from glassy water except at the glass transition temperature and above. Moreover, the molecular dynamics simulation shows no evidence for the formation of a high-<span class="hlt">density</span> phase when depositing water molecules at very low temperature. In order to model the processing of interstellar <span class="hlt">ices</span> by cosmic ray protons and heavy ions coming from the magnetospheric radiation environment around the giant planets, we bombarded samples of vitreous <span class="hlt">ice</span> and cubic <span class="hlt">ice</span> with 35 eV water molecules. After irradiation the recovered samples were found to be densified, the lower the temperature, the higher the <span class="hlt">density</span> of the recovered sample. The analysis of the structure and vibrational properties of this new high-<span class="hlt">density</span> phase of amorphous <span class="hlt">ice</span> shows a close relationship with those of high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> obtained by pressure-induced amorphization. Copyright 2004 American Institute of Physics</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5339F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5339F"><span>Assessing the accuracy of Greenland <span class="hlt">ice</span> sheet <span class="hlt">ice</span> ablation measurements by pressure transducer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fausto, R. S.; van As, D.; Ahlstrøm, A. P.</p> <p>2012-04-01</p> <p>In the glaciological community there is a need for reliable <span class="hlt">mass</span> balance measurements of glaciers and <span class="hlt">ice</span> sheets, ranging from daily to yearly time scales. Here we present a method to measure <span class="hlt">ice</span> ablation using a pressure transducer. The pressure transducer is drilled into the <span class="hlt">ice</span>, en-closed in a hose filled with a liquid that is non-freezable at common Greenlandic temperatures. The pressure signal registered by the transducer is that of the vertical column of liquid over the sensor, which can be translated in depth knowing the <span class="hlt">density</span> of the liquid. As the free-standing AWS moves down with the ablating surface and the hose melts out of the <span class="hlt">ice</span>, an increasingly large part of the hose will lay flat on the <span class="hlt">ice</span> surface, and the hydrostatic pressure from the vertical column of liquid in the hose will get smaller. This reduction in pressure provides us with the ablation rate. By measuring at (sub-) daily timescales this assembly is well-suited to monitor <span class="hlt">ice</span> ablation in remote regions, with clear advantages over other well-established methods of measuring <span class="hlt">ice</span> ablation in the field. The pressure transducer system has the potential to monitor <span class="hlt">ice</span> ablation for several years without re-drilling and the system is suitable for high ablation areas. A routine to transform raw measurements into ablation values will also be presented, including a physically based method to remove air pressure variability from the signal. The pressure transducer time-series is compared to that recorded by a sonic ranger for the climatically hostile setting on the Greenland <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2501P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2501P"><span><span class="hlt">Ice</span> core evidence for a 20th century increase in surface <span class="hlt">mass</span> balance in coastal Dronning Maud Land, East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Philippe, Morgane; Tison, Jean-Louis; Fjøsne, Karen; Hubbard, Bryn; Kjær, Helle A.; Lenaerts, Jan T. M.; Drews, Reinhard; Sheldon, Simon G.; De Bondt, Kevin; Claeys, Philippe; Pattyn, Frank</p> <p>2016-10-01</p> <p><span class="hlt">Ice</span> cores provide temporal records of surface <span class="hlt">mass</span> balance (SMB). Coastal areas of Antarctica have relatively high and variable SMB, but are under-represented in records spanning more than 100 years. Here we present SMB reconstruction from a 120 m-long <span class="hlt">ice</span> core drilled in 2012 on the Derwael <span class="hlt">Ice</span> Rise, coastal Dronning Maud Land, East Antarctica. Water stable isotope (δ18O and δD) stratigraphy is supplemented by discontinuous major ion profiles and continuous electrical conductivity measurements. The base of the <span class="hlt">ice</span> core is dated to AD 1759 ± 16, providing a climate proxy for the past ˜ 250 years. The core's annual layer thickness history is combined with its gravimetric <span class="hlt">density</span> profile to reconstruct the site's SMB history, corrected for the influence of <span class="hlt">ice</span> deformation. The mean SMB for the core's entire history is 0.47 ± 0.02 m water equivalent (w.e.) a-1. The time series of reconstructed annual SMB shows high variability, but a general increase beginning in the 20th century. This increase is particularly marked during the last 50 years (1962-2011), which yields mean SMB of 0.61 ± 0.01 m w.e. a-1. This trend is compared with other reported SMB data in Antarctica, generally showing a high spatial variability. Output of the fully coupled Community Earth System Model (CESM) suggests that, although atmospheric circulation is the main factor influencing SMB, variability in sea surface temperatures and sea <span class="hlt">ice</span> cover in the precipitation source region also explain part of the variability in SMB. Local snow redistribution can also influence interannual variability but is unlikely to influence long-term trends significantly. This is the first record from a coastal <span class="hlt">ice</span> core in East Antarctica to show an increase in SMB beginning in the early 20th century and particularly marked during the last 50 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930062304&hterms=mit+sloan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmit%2Bsloan','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930062304&hterms=mit+sloan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmit%2Bsloan"><span>IRAS galaxies versus POTENT <span class="hlt">mass</span> - <span class="hlt">Density</span> fields, biasing, and Omega</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dekel, Avishai; Bertschinger, Edmund; Yahil, Amos; Strauss, Michael A.; Davis, Marc; Huchra, John P.</p> <p>1993-01-01</p> <p>A comparison of the galaxy <span class="hlt">density</span> field extracted from a complete redshift survey of IRAS galaxies brighter than 1.936 Jy with the <span class="hlt">mass-density</span> field reconstructed by the POTENT procedure from the observed peculiar velocities of 493 objects is presented. A strong correlation is found between the galaxy and <span class="hlt">mass-density</span> fields; both feature the Great Attractor, part of the Perseus-Pisces supercluster, and the large void between them. Monte Carlo noise simulations show that the data are consistent with the hypotheses that the smoothed fluctuations of galaxy and <span class="hlt">mass</span> <span class="hlt">densities</span> at each point are proportional to each other with the 'biasing' factor of IRAS galaxies, b(I), and that the peculiar velocity field is related to the <span class="hlt">mass-density</span> field as expected according to the gravitational instability theory. Under these hypotheses, the two <span class="hlt">density</span> fields can be related by specifying b(I) and the cosmological <span class="hlt">density</span> parameter, Omega.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3950934','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3950934"><span>IR-MALDESI <span class="hlt">MASS</span> SPECTROMETRY IMAGING OF BIOLOGICAL TISSUE SECTIONS USING <span class="hlt">ICE</span> AS A MATRIX</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Robichaud, Guillaume; Barry, Jeremy A.; Muddiman, David C.</p> <p>2014-01-01</p> <p>Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) <span class="hlt">Mass</span> Spectrometry imaging of biological tissue sections using a layer of deposited <span class="hlt">ice</span> as an energy absorbing matrix was investigated. Dynamics of plume ablation were first explored using a nanosecond exposure shadowgraphy system designed to simultaneously collect pictures of the plume with a camera and collect the FT-ICR <span class="hlt">mass</span> spectrum corresponding to that same ablation event. Ablation of fresh tissue analyzed with and without using <span class="hlt">ice</span> as a matrix were both compared using this technique. Effect of spot-to-spot distance, number of laser shots per pixel and tissue condition (matrix) on ion abundance was also investigated for 50 µm thick tissue sections. Finally, the statistical method called design of experiments was used to compare source parameters and determine the optimal conditions for IR-MALDESI of tissue sections using deposited <span class="hlt">ice</span> as a matrix. With a better understanding of the fundamentals of ablation dynamics and a systematic approach to explore the experimental space, it was possible to improve ion abundance by nearly one order of magnitude. PMID:24385399</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33B0793I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33B0793I"><span>Spatiotemporal Patterns of <span class="hlt">Ice</span> <span class="hlt">Mass</span> Variations and the Local Climatic Factors in the Riparian Zone of Central Valley, California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inamdar, P.; Ambinakudige, S.</p> <p>2016-12-01</p> <p>Californian icefields are natural basins of fresh water. They provide irrigation water to the farms in the central valley. We analyzed the <span class="hlt">ice</span> <span class="hlt">mass</span> loss rates, air temperature and land surface temperature (LST) in Sacramento and San Joaquin basins in California. The digital elevation models from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were used to calculate <span class="hlt">ice</span> <span class="hlt">mass</span> loss rate between the years 2002 and 2015. Additionally, Landsat TIR data were used to extract the land surface temperature. Data from local weather stations were analyzed to understand the spatiotemporal trends in air temperature. The results showed an overall <span class="hlt">mass</span> recession of -0.8 ± 0.7 m w.e.a-1. We also noticed an about 60% loss in areal extent of the glaciers in the study basins between 2000 and 2015. Local climatic factors, along with the global climate patterns might have influenced the negative trends in the <span class="hlt">ice</span> <span class="hlt">mass</span> loss. Overall, there was an increase in the air temperature by 0.07± 0.02 °C in the central valley between 2000 and 2015. Furthermore, LST increased by 0.34 ± 0.4 °C and 0.55± 0.1 °C in the Sacramento and San Joaquin basins. Our preliminary results show the decrease in area and <span class="hlt">mass</span> of <span class="hlt">ice</span> <span class="hlt">mass</span> in the basins, and changing agricultural practices in the valley.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C11D0699A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C11D0699A"><span>Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet - <span class="hlt">Ice</span> Surface Velocities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andersen, S. B.; Ahlstrom, A. P.; Boncori, J. M.; Dall, J.</p> <p>2011-12-01</p> <p>In 2007, the Danish Ministry of Climate and Energy launched the Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet (PROMICE) as an ongoing effort to assess changes in the <span class="hlt">mass</span> budget of the Greenland <span class="hlt">Ice</span> Sheet. Iceberg calving from the outlet glaciers of the Greenland <span class="hlt">Ice</span> Sheet, often termed the <span class="hlt">ice</span>-dynamic <span class="hlt">mass</span> loss, is responsible for an important part of the <span class="hlt">mass</span> loss during the last decade. To quantify this part of the <span class="hlt">mass</span> loss, we combine airborne surveys yielding <span class="hlt">ice</span>-sheet thickness along the entire margin, with surface velocities derived from satellite synthetic-aperture radar (SAR). In order to derive <span class="hlt">ice</span> sheet surface velocities from SAR a processing chain has been developed for GEUS by DTU Space based on a commercial software package distributed by GAMMA Remote Sensing. The processor, named SUSIE (Scripts and Utilities for SAR <span class="hlt">Ice</span>-motion Estimation), can use both differential SAR interferometry and offset-tracking techniques to measure the horizontal velocity components, providing also an estimate of the corresponding measurement error. So far surface velocities have been derived for a number of sites including Nioghalvfjerdsfjord Glacier, the Kangerlussuaq region, the Nuuk region, Helheim Glacier and Daugaard-Jensen Glacier using data from ERS-1/ERS-2, ENVISAT ASAR and ALOS Palsar. Here we will present these first results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3917821','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3917821"><span><span class="hlt">Ice</span> hockey lung – a case of <span class="hlt">mass</span> nitrogen dioxide poisoning in the Czech Republic</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brat, Kristian; Merta, Zdenek; Plutinsky, Marek; Skrickova, Jana; Ing, Miroslav Stanek</p> <p>2013-01-01</p> <p>Nitrogen dioxide (NO2) is a toxic gas, a product of combustion in malfunctioning <span class="hlt">ice</span>-resurfacing machines. NO2 poisoning is rare but potentially lethal. The authors report a case of <span class="hlt">mass</span> NO2 poisoning involving 15 amateur <span class="hlt">ice</span> hockey players in the Czech Republic. All players were treated in the Department of Respiratory Diseases at Brno University Hospital in November 2010 – three as inpatients because they developed pneumonitis. All patients were followed-up until November 2011. Complete recovery in all but one patient was achieved by December 2010. None of the 15 patients developed asthma-like disease or chronic cough. Corticosteroids appeared to be useful in treatment. Electric-powered <span class="hlt">ice</span>-resurfacing machines are preferable in indoor <span class="hlt">ice</span> skating arenas. PMID:24032121</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22253455-novel-two-step-laser-ablation-ionization-mass-spectrometry-laims-actor-spectator-ice-layers-probing-chemical-composition-sub-ice-beneath-sub-ice-layer','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22253455-novel-two-step-laser-ablation-ionization-mass-spectrometry-laims-actor-spectator-ice-layers-probing-chemical-composition-sub-ice-beneath-sub-ice-layer"><span>Novel two-step laser ablation and ionization <span class="hlt">mass</span> spectrometry (2S-LAIMS) of actor-spectator <span class="hlt">ice</span> layers: Probing chemical composition of D{sub 2}O <span class="hlt">ice</span> beneath a H{sub 2}O <span class="hlt">ice</span> layer</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Yang, Rui, E-mail: ryang73@ustc.edu; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov</p> <p>2014-03-14</p> <p>In this work, we report for the first time successful analysis of organic aromatic analytes imbedded in D{sub 2}O <span class="hlt">ices</span> by novel infrared (IR) laser ablation of a layered non-absorbing D{sub 2}O <span class="hlt">ice</span> (spectator) containing the analytes and an ablation-active IR-absorbing H{sub 2}O <span class="hlt">ice</span> layer (actor) without the analyte. With these studies we have opened up a new method for the in situ analysis of solids containing analytes when covered with an IR laser-absorbing layer that can be resonantly ablated. This soft ejection method takes advantage of the tenability of two-step infrared laser ablation and ultraviolet laser ionization <span class="hlt">mass</span> spectrometry,more » previously demonstrated in this lab to study chemical reactions of polycyclic aromatic hydrocarbons (PAHs) in cryogenic <span class="hlt">ices</span>. The IR laser pulse tuned to resonantly excite only the upper H{sub 2}O <span class="hlt">ice</span> layer (actor) generates a shockwave upon impact. This shockwave penetrates the lower analyte-containing D{sub 2}O <span class="hlt">ice</span> layer (spectator, a non-absorbing <span class="hlt">ice</span> that cannot be ablated directly with the wavelength of the IR laser employed) and is reflected back, ejecting the contents of the D{sub 2}O layer into the vacuum where they are intersected by a UV laser for ionization and detection by a time-of-flight <span class="hlt">mass</span> spectrometer. Thus, energy is transmitted from the laser-absorbing actor layer into the non-absorbing spectator layer resulting its ablation. We found that isotope cross-contamination between layers was negligible. We also did not see any evidence for thermal or collisional chemistry of PAH molecules with H{sub 2}O molecules in the shockwave. We call this “shockwave mediated surface resonance enhanced subsurface ablation” technique as “two-step laser ablation and ionization <span class="hlt">mass</span> spectrometry of actor-spectator <span class="hlt">ice</span> layers.” This method has its roots in the well-established MALDI (matrix assisted laser desorption and ionization) method. Our method offers more flexibility to optimize both the processes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1273R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1273R"><span>Changing pattern of <span class="hlt">ice</span> flow and <span class="hlt">mass</span> balance for glaciers discharging into the Larsen A and B embayments, Antarctic Peninsula, 2011 to 2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rott, Helmut; Abdel Jaber, Wael; Wuite, Jan; Scheiblauer, Stefan; Floricioiu, Dana; Melchior van Wessem, Jan; Nagler, Thomas; Miranda, Nuno; van den Broeke, Michiel R.</p> <p>2018-04-01</p> <p>We analysed volume change and <span class="hlt">mass</span> balance of outlet glaciers on the northern Antarctic Peninsula over the periods 2011 to 2013 and 2013 to 2016, using high-resolution topographic data from the bistatic interferometric radar satellite mission TanDEM-X. Complementary to the geodetic method that applies DEM differencing, we computed the net <span class="hlt">mass</span> balance of the main outlet glaciers using the <span class="hlt">mass</span> budget method, accounting for the difference between the surface <span class="hlt">mass</span> balance (SMB) and the discharge of <span class="hlt">ice</span> into an ocean or <span class="hlt">ice</span> shelf. The SMB values are based on output of the regional climate model RACMO version 2.3p2. To study glacier flow and retrieve <span class="hlt">ice</span> discharge we generated time series of <span class="hlt">ice</span> velocity from data from different satellite radar sensors, with radar images of the satellites TerraSAR-X and TanDEM-X as the main source. The study area comprises tributaries to the Larsen A, Larsen Inlet and Prince Gustav Channel embayments (region A), the glaciers calving into the Larsen B embayment (region B) and the glaciers draining into the remnant part of the Larsen B <span class="hlt">ice</span> shelf in Scar Inlet (region C). The glaciers of region A, where the buttressing <span class="hlt">ice</span> shelf disintegrated in 1995, and of region B (<span class="hlt">ice</span> shelf break-up in 2002) show continuing losses in <span class="hlt">ice</span> <span class="hlt">mass</span>, with significant reduction of losses after 2013. The <span class="hlt">mass</span> balance numbers for the grounded glacier area of region A are -3.98 ± 0.33 Gt a-1 from 2011 to 2013 and -2.38 ± 0.18 Gt a-1 from 2013 to 2016. The corresponding numbers for region B are -5.75 ± 0.45 and -2.32 ± 0.25 Gt a-1. The <span class="hlt">mass</span> balance in region C during the two periods was slightly negative, at -0.54 ± 0.38 Gt a-1 and -0.58 ± 0.25 Gt a-1. The main share in the overall <span class="hlt">mass</span> losses of the region was contributed by two glaciers: Drygalski Glacier contributing 61 % to the <span class="hlt">mass</span> deficit of region A, and Hektoria and Green glaciers accounting for 67 % to the <span class="hlt">mass</span> deficit of region B. Hektoria and Green glaciers accelerated significantly in 2010</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C53B0574L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C53B0574L"><span><span class="hlt">Ice</span> Shelf-Ocean Interactions Near <span class="hlt">Ice</span> Rises and <span class="hlt">Ice</span> Rumples</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lange, M. A.; Rückamp, M.; Kleiner, T.</p> <p>2013-12-01</p> <p>The stability of <span class="hlt">ice</span> shelves depends on the existence of embayments and is largely influenced by <span class="hlt">ice</span> rises and <span class="hlt">ice</span> rumples, which act as 'pinning-points' for <span class="hlt">ice</span> shelf movement. Of additional critical importance are interactions between <span class="hlt">ice</span> shelves and the water <span class="hlt">masses</span> underlying them in <span class="hlt">ice</span> shelf cavities, particularly melting and refreezing processes. The present study aims to elucidate the role of <span class="hlt">ice</span> rises and <span class="hlt">ice</span> rumples in the context of climate change impacts on Antarctic <span class="hlt">ice</span> shelves. However, due to their smaller spatial extent, <span class="hlt">ice</span> rumples react more sensitively to climate change than <span class="hlt">ice</span> rises. Different forcings are at work and need to be considered separately as well as synergistically. In order to address these issues, we have decided to deal with the following three issues explicitly: oceanographic-, cryospheric and general topics. In so doing, we paid particular attention to possible interrelationships and feedbacks in a coupled <span class="hlt">ice</span>-shelf-ocean system. With regard to oceanographic issues, we have applied the ocean circulation model ROMBAX to ocean water <span class="hlt">masses</span> adjacent to and underneath a number of idealized <span class="hlt">ice</span> shelf configurations: wide and narrow as well as laterally restrained and unrestrained <span class="hlt">ice</span> shelves. Simulations were performed with and without small <span class="hlt">ice</span> rises located close to the calving front. For larger configurations, the impact of the <span class="hlt">ice</span> rises on melt rates at the <span class="hlt">ice</span> shelf base is negligible, while for smaller configurations net melting rates at the <span class="hlt">ice</span>-shelf base differ by a factor of up to eight depending on whether <span class="hlt">ice</span> rises are considered or not. We employed the thermo-coupled <span class="hlt">ice</span> flow model TIM-FD3 to simulate the effects of several <span class="hlt">ice</span> rises and one <span class="hlt">ice</span> rumple on the dynamics of <span class="hlt">ice</span> shelf flow. We considered the complete un-grounding of the <span class="hlt">ice</span> shelf in order to investigate the effect of pinning points of different characteristics (interior or near calving front, small and medium sized) on the resulting flow and stress fields</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920030077&hterms=seeds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dseeds','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920030077&hterms=seeds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dseeds"><span>Statistics of primordial <span class="hlt">density</span> perturbations from discrete seed <span class="hlt">masses</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scherrer, Robert J.; Bertschinger, Edmund</p> <p>1991-01-01</p> <p>The statistics of <span class="hlt">density</span> perturbations for general distributions of seed <span class="hlt">masses</span> with arbitrary matter accretion is examined. Formal expressions for the power spectrum, the N-point correlation functions, and the <span class="hlt">density</span> distribution function are derived. These results are applied to the case of uncorrelated seed <span class="hlt">masses</span>, and power spectra are derived for accretion of both hot and cold dark matter plus baryons. The reduced moments (cumulants) of the <span class="hlt">density</span> distribution are computed and used to obtain a series expansion for the <span class="hlt">density</span> distribution function. Analytic results are obtained for the <span class="hlt">density</span> distribution function in the case of a distribution of seed <span class="hlt">masses</span> with a spherical top-hat accretion pattern. More generally, the formalism makes it possible to give a complete characterization of the statistical properties of any random field generated from a discrete linear superposition of kernels. In particular, the results can be applied to <span class="hlt">density</span> fields derived by smoothing a discrete set of points with a window function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.1965S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.1965S"><span>Application of GRACE to the assessment of model-based estimates of monthly Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">mass</span> balance (2003-2012)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlegel, Nicole-Jeanne; Wiese, David N.; Larour, Eric Y.; Watkins, Michael M.; Box, Jason E.; Fettweis, Xavier; van den Broeke, Michiel R.</p> <p>2016-09-01</p> <p>Quantifying the Greenland <span class="hlt">Ice</span> Sheet's future contribution to sea level rise is a challenging task that requires accurate estimates of <span class="hlt">ice</span> sheet sensitivity to climate change. Forward <span class="hlt">ice</span> sheet models are promising tools for estimating future <span class="hlt">ice</span> sheet behavior, yet confidence is low because evaluation of historical simulations is challenging due to the scarcity of continental-wide data for model evaluation. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained <span class="hlt">mass</span> concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of monthly global gravity fields. Specifically, the Jet Propulsion Laboratory's JPL RL05M GRACE mascon solution (GRACE_JPL) offers an opportunity for the assessment of model-based estimates of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance (MB) at ˜ 300 km spatial scales. Here, we quantify the differences between Greenland monthly observed MB (GRACE_JPL) and that estimated by state-of-the-art, high-resolution models, with respect to GRACE_JPL and model uncertainties. To simulate the years 2003-2012, we force the <span class="hlt">Ice</span> Sheet System Model (ISSM) with anomalies from three different surface <span class="hlt">mass</span> balance (SMB) products derived from regional climate models. Resulting MB is compared against GRACE_JPL within individual mascons. Overall, we find agreement in the northeast and southwest where MB is assumed to be primarily controlled by SMB. In the interior, we find a discrepancy in trend, which we presume to be related to millennial-scale dynamic thickening not considered by our model. In the northwest, seasonal amplitudes agree, but modeled <span class="hlt">mass</span> trends are muted relative to GRACE_JPL. Here, discrepancies are likely controlled by temporal variability in <span class="hlt">ice</span> discharge and other related processes not represented by our model simulations, i.e., hydrological processes and <span class="hlt">ice</span>-ocean interaction. In the southeast, GRACE_JPL exhibits larger seasonal amplitude than predicted by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.U44A..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.U44A..01A"><span>Recent Changes in Arctic Glaciers, <span class="hlt">Ice</span> Caps, and the Greenland <span class="hlt">Ice</span> Sheet: Cold Facts About Warm <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdalati, W.</p> <p>2005-12-01</p> <p>One of the major manifestations of Arctic change can be observed in the state of balance of Arctic glaciers and <span class="hlt">ice</span> caps and the Greenland <span class="hlt">ice</span> sheet. These <span class="hlt">ice</span> <span class="hlt">masses</span> are estimated to contain nearly 3 million cubic kilometers of <span class="hlt">ice</span>, which is more than six times greater than all the water stored in the Earth's lakes, rivers, and snow combined and is the equivalent of over 7 meters of sea level. Most of these <span class="hlt">ice</span> <span class="hlt">masses</span> have been shrinking in recent in years, but their <span class="hlt">mass</span> balance is highly variable on a wide range of spatial and temporal scales. On the Greenland <span class="hlt">ice</span> sheet most of the coastal regions have thinned substantially as melt has increased and some of its outlet glaciers have accelerated. Near the equilibrium line in West Greenland, we have seen evidence of summer acceleration that is linked to surface meltwater production, suggesting a relatively rapid response mechanism of the <span class="hlt">ice</span> sheet change to a warming climate. At the same time, however, the vast interior regions of the Greenland <span class="hlt">ice</span> sheet have shown little change or slight growth, as accumulation in these areas may have increased. Throughout much of the rest of the Arctic, many glaciers and <span class="hlt">ice</span> caps have been shrinking in the past few decades, and in Canada and Alaska, the rate of <span class="hlt">ice</span> loss seems to have accelerated during the late 1990s. These recent observations offer only a snapshot in time of the long-term behavior, but they are providing crucial information about the current state of <span class="hlt">ice</span> <span class="hlt">mass</span> balance and the mechanisms that control it in one of the most climatically sensitive regions on Earth. As we continue to learn more through a combination of remote sensing observations, in situ measurements and improved modeling capabilities, it is important that we coordinate and integrate these approaches effectively in order to predict future changes and their impact on sea level, freshwater discharge, and ocean circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C54A..05H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C54A..05H"><span>Snow, Firn and <span class="hlt">Ice</span> Heterogeneity within Larsen C <span class="hlt">Ice</span> Shelf Revealed by Borehole Optical-televiewing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hubbard, B. P.; Ashmore, D.; Luckman, A. J.; Kulessa, B.; Bevan, S. L.; Booth, A.; Kuipers Munneke, P.; O'Leary, M.; Sevestre, H.</p> <p>2016-12-01</p> <p>The north-western sector of Larsen C <span class="hlt">Ice</span> Shelf (LCIS), Antarctica, hosts intermittent surface ponds resulting from intense melting, largely driven by warm föhn winds. The fate of such surface melt water is largely controlled by the shelf's firn structure, which also dictates shelf <span class="hlt">density</span> (widely used to reconstruct <span class="hlt">ice</span> shelf thickness from altimetric data) and preconditioning to hydrofracture. Here, we report a suite of five 90 m long optical-televiewer (OPTV) borehole logs from the northern and central regions of LCIS recorded in spring 2014 and 2015. For each OPTV log we reconstruct vertical variations in material <span class="hlt">density</span> via an empirical OPTV log-<span class="hlt">ice</span> core calibration, and apply a thresholding technique to estimate refrozen <span class="hlt">ice</span> content within the firn column. These data are combined to define five material facies present within this sector of LCIS. The firn/<span class="hlt">ice</span> column is anomalously dense at all five sites, having an overall mean depth-averaged <span class="hlt">density</span> of 873 +/-32 kg m-3. In terms of spatial variability, our findings generally support previous estimates of firn air content fields and implied infiltration <span class="hlt">ice</span> content. However, they also highlight finer-resolution complexity of <span class="hlt">ice</span> shelf structure. For example, the most dense <span class="hlt">ice</span>, with the lowest equivalent firn air content, is not located within the most westerly inlets, where firn-driven melting and ponding are most active, but some tens of km down-flow of these areas. We interpret this effect in terms of the inheritance nearer the grounding line of relatively low-<span class="hlt">density</span> glacial <span class="hlt">ice</span> (e.g., 52 m thick with a <span class="hlt">density</span> of 852 +/-21 kg m-3 in northernmost Cabinet Inlet) advected from inland. This inherited <span class="hlt">ice</span> forms one of five facies identified across the study region. These are, extending broadly downwards into the shelf, and with different representation at each site: local accumulation (F1); local accumulation hosting substantial infiltration <span class="hlt">ice</span>, i.e. influenced by intense melt but insufficient to form</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170004574&hterms=antarctica+mean&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWhat%2Bantarctica%2Bmean','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170004574&hterms=antarctica+mean&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWhat%2Bantarctica%2Bmean"><span><span class="hlt">Ice</span> <span class="hlt">Mass</span> Change in Greenland and Antarctica Between 1993 and 2013 from Satellite Gravity Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Talpe, Matthieu J.; Nerem, R. Steven; Forootan, Ehsan; Schmidt, Michael; Lemoine, Frank G.; Enderlin, Ellyn M.; Landerer, Felix W.</p> <p>2017-01-01</p> <p>We construct long-term time series of Greenland and Antarctic <span class="hlt">ice</span> sheet <span class="hlt">mass</span> change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of <span class="hlt">mass</span> variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of <span class="hlt">mass</span> loss than other methods before 2000, while the Antarctic <span class="hlt">ice</span> sheet appears heavily influenced by interannual variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ACP....14.1205J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ACP....14.1205J"><span>On the relationship between Arctic <span class="hlt">ice</span> clouds and polluted air <span class="hlt">masses</span> over the North Slope of Alaska in April 2008</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jouan, C.; Pelon, J.; Girard, E.; Ancellet, G.; Blanchet, J. P.; Delanoë, J.</p> <p>2014-02-01</p> <p>Recently, two types of <span class="hlt">ice</span> clouds (TICs) properties have been characterized using the Indirect and Semi-Direct Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L-1) and larger (> 110 μm) <span class="hlt">ice</span> crystals, and a larger <span class="hlt">ice</span> supersaturation (> 15%) compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the <span class="hlt">ice</span> nucleating properties of <span class="hlt">ice</span> nuclei (IN) through acidification, resulting in a smaller concentration of larger <span class="hlt">ice</span> crystals and leading to precipitation (e.g., cloud regime TIC-2B). Here, the origin of air <span class="hlt">masses</span> forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air <span class="hlt">masses</span> transport from three potential SO2 emission sources into Alaska: eastern China and Siberia where anthropogenic and biomass burning emissions, respectively, are produced, and the volcanic region of the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China and Siberia over Alaska, most probably with the contribution of acidic volcanic aerosol during the TIC-2B period. Observation Monitoring Instrument (OMI) satellite observations reveal that SO2 concentrations in air <span class="hlt">masses</span> forming the TIC-2B were larger than in air <span class="hlt">masses</span> forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results support the hypothesis that acidic coating on IN could be at the origin of the formation of TIC-2B.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11607393','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11607393"><span>Galaxy dynamics and the <span class="hlt">mass</span> <span class="hlt">density</span> of the universe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rubin, V C</p> <p>1993-06-01</p> <p>Dynamical evidence accumulated over the past 20 years has convinced astronomers that luminous matter in a spiral galaxy constitutes no more than 10% of the <span class="hlt">mass</span> of a galaxy. An additional 90% is inferred by its gravitational effect on luminous material. Here I review recent observations concerning the distribution of luminous and nonluminous matter in the Milky Way, in galaxies, and in galaxy clusters. Observations of neutral hydrogen disks, some extending in radius several times the optical disk, confirm that a massive dark halo is a major component of virtually every spiral. A recent surprise has been the discovery that stellar and gas motions in ellipticals are enormously complex. To date, only for a few spheroidal galaxies do the velocities extend far enough to probe the outer <span class="hlt">mass</span> distribution. But the diverse kinematics of inner cores, peripheral to deducing the overall <span class="hlt">mass</span> distribution, offer additional evidence that ellipticals have acquired gas-rich systems after initial formation. Dynamical results are consistent with a low-<span class="hlt">density</span> universe, in which the required dark matter could be baryonic. On smallest scales of galaxies [10 kiloparsec (kpc); Ho = 50 km.sec-1.megaparsec-1] the luminous matter constitutes only 1% of the closure <span class="hlt">density</span>. On scales greater than binary galaxies (i.e., >/=100 kpc) all systems indicate a <span class="hlt">density</span> approximately 10% of the closure <span class="hlt">density</span>, a <span class="hlt">density</span> consistent with the low baryon <span class="hlt">density</span> in the universe. If large-scale motions in the universe require a higher <span class="hlt">mass</span> <span class="hlt">density</span>, these motions would constitute the first dynamical evidence for nonbaryonic matter in a universe of higher <span class="hlt">density</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.C41A..02R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.C41A..02R"><span>Leakage of the Greenland <span class="hlt">Ice</span> Sheet through accelerated <span class="hlt">ice</span> flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.</p> <p>2005-12-01</p> <p>A map of coastal velocities of the Greenland <span class="hlt">ice</span> sheet was produced from Radarsat-1 acquired during the background mission of 2000 and combined with radio echo sounding data to estimate the <span class="hlt">ice</span> discharge from the <span class="hlt">ice</span> sheet. On individual glaciers, <span class="hlt">ice</span> discharge was compared with snow input from the interior and melt above the flux gate to determine the glacier <span class="hlt">mass</span> balance. Time series of velocities on several glaciers at different latitudes reveal seasonal fluctuations of only 7-8 percent so that winter velocities are only 2 percent less than the yearly mean. The results show the northern Greenland glaciers to be close to balance yet losing <span class="hlt">mass</span>. No change in <span class="hlt">ice</span> flow is detected on Petermann, 79north and Zachariae Isstrom in 2000-2004. East Greenland glaciers are in balance and flowing steadily north of Kangerdlussuaq, but Kangerdlussuaq, Helheim and all the southeastern glaciers are thinning dramatically. All these glaciers accelerated, Kangerdlussuaq in 2000, Helheim prior to 2004, and southeast Greenland glaciers accelerated 10 to 50 percent in 2000-2004. Glacier acceleration is generally brutal, probably once the glacier reached a threshold, and sustained. In the northwest, most glaciers are largely out of balance. Jakobshavn accelerated significantly in 2002, and glaciers in its immediate vicinity accelerated more than 50 percent in 2000-2004. Less is known about southwest Greenland glaciers due to a lack of <span class="hlt">ice</span> thickness data but the glaciers have accelerated there as well and are likely to be strongly out of balance despite thickening of the interior. Overall, I estimate the <span class="hlt">mass</span> balance of the Greenland <span class="hlt">ice</span> sheet to be about -80 +/-10 cubic km of <span class="hlt">ice</span> per year in 2000 and -110 +/-15 cubic km of <span class="hlt">ice</span> per year in 2004, i.e. more negative than based on partial altimetry surveys of the outlet glaciers. As climate continues to warm, more glaciers will accelerate, and the <span class="hlt">mass</span> balance will become increasingly negative, regardless of the evolution of the <span class="hlt">ice</span> sheet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1579W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1579W"><span>Early 21st-Century <span class="hlt">Mass</span> loss of the North-Atlantic Glaciers and <span class="hlt">Ice</span> Caps (Arne Richter Award for Outstanding Young Scientists Lecture)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wouters, Bert; Ligtenberg, Stefan; Moholdt, Geir; Gardner, Alex S.; Noel, Brice; Kuipers Munneke, Peter; van den Broeke, Michiel; Bamber, Jonathan L.</p> <p>2016-04-01</p> <p>Historically, <span class="hlt">ice</span> loss from mountain glaciers and <span class="hlt">ice</span> caps has been one of the largest contributors to sea level rise over the last century. Of particular interest are the glaciers and <span class="hlt">ice</span> caps in the North-Atlantic region of the Arctic. Despite the cold climate in this area, considerable melting and runoff occurs in summer. A small increase in temperature will have an immediate effect on these processes, so that a large change in the Arctic <span class="hlt">ice</span> volume can be expected in response to the anticipated climate change in the coming century. Unfortunately, direct observations of glaciers are sparse and are biased toward glaciers systems in accessible, mostly maritime, climate conditions. Remote sensing is therefore essential to monitor the state of the the North-Atlantic glaciers and <span class="hlt">ice</span> caps. In this presentation, we will discuss the progress that has been made in estimating the <span class="hlt">ice</span> <span class="hlt">mass</span> balance of these regions, with a particular focus on measurements made by ESA's Cryosat-2 radar altimeter mission (2010-present). Compared to earlier altimeter mission, Cryosat-2 provides unprecedented coverage of the cryosphere, with a resolution down to 1 km or better and sampling at monthly intervals. Combining the Cryosat-2 measurements with the laser altimetry data from ICESat (2003-2009) gives us a 12 yr time series of glacial <span class="hlt">mass</span> loss in the North Atlantic. We find excellent agreement between the altimetry measurements and independent observations by the GRACE mission, which directly 'weighs' the <span class="hlt">ice</span> caps, albeit at a much lower resolution. <span class="hlt">Mass</span> loss in the region has increased from 120 Gigatonnes per year in 2003-2009 to roughly 140 Gt/yr in 2010-2014, with an important contribution from Greenland's peripheral glaciers and <span class="hlt">ice</span> caps. Importantly, the <span class="hlt">mass</span> loss is not stationary, but shows large regional interannual variability, with <span class="hlt">mass</span> loss shifting between eastern and western regions from year to year. Comparison with regional climate models shows that these shifts can be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..12113559S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..12113559S"><span><span class="hlt">Ice</span> nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina, and Germany</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steinke, I.; Funk, R.; Busse, J.; Iturri, A.; Kirchen, S.; Leue, M.; Möhler, O.; Schwartz, T.; Schnaiter, M.; Sierau, B.; Toprak, E.; Ullrich, R.; Ulrich, A.; Hoose, C.; Leisner, T.</p> <p>2016-11-01</p> <p>Soil dust particles emitted from agricultural areas contain considerable <span class="hlt">mass</span> fractions of organic material. Also, soil dust particles may act as carriers for potentially <span class="hlt">ice</span>-active biological particles. In this work, we present <span class="hlt">ice</span> nucleation experiments conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber. We investigated the <span class="hlt">ice</span> nucleation efficiency of four types of soil dust from different regions of the world. The results are expressed as <span class="hlt">ice</span> nucleation active surface site (INAS) <span class="hlt">densities</span> and presented for the immersion freezing and the deposition nucleation mode. For immersion freezing occurring at 254 K, samples from Argentina, China, and Germany show <span class="hlt">ice</span> nucleation efficiencies which are by a factor of 10 higher than desert dusts. On average, the difference in <span class="hlt">ice</span> nucleation efficiencies between agricultural and desert dusts becomes significantly smaller at temperatures below 247 K. In the deposition mode the soil dusts showed higher <span class="hlt">ice</span> nucleation activity than Arizona Test Dust over a temperature range between 232 and 248 K and humidities RHice up to 125%. INAS <span class="hlt">densities</span> varied between 109 and 1011 m-2 for these thermodynamic conditions. For one soil dust sample (Argentinian Soil), the effect of treatments with heat was investigated. Heat treatments (383 K) did not affect the <span class="hlt">ice</span> nucleation efficiency observed at 249 K. This finding presumably excludes proteinaceous <span class="hlt">ice</span>-nucleating entities as the only source of the increased <span class="hlt">ice</span> nucleation efficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...849...30C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...849...30C"><span>Steamworlds: Atmospheric Structure and Critical <span class="hlt">Mass</span> of Planets Accreting Icy Pebbles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chambers, John</p> <p>2017-11-01</p> <p>In the core accretion model, gas-giant planets first form a solid core, which then accretes gas from a protoplanetary disk when the core exceeds a critical <span class="hlt">mass</span>. Here, we model the atmosphere of a core that grows by accreting <span class="hlt">ice</span>-rich pebbles. The <span class="hlt">ice</span> fraction of pebbles evaporates in warm regions of the atmosphere, saturating it with water vapor. Excess water precipitates to lower altitudes. Beneath an outer radiative region, the atmosphere is convective, following a moist adiabat in saturated regions due to water condensation and precipitation. Atmospheric <span class="hlt">mass</span>, <span class="hlt">density</span>, and temperature increase with core <span class="hlt">mass</span>. For nominal model parameters, planets with core <span class="hlt">masses</span> (<span class="hlt">ice</span> + rock) between 0.08 and 0.16 Earth <span class="hlt">masses</span> have surface temperatures between 273 and 647 K and form an ocean. In more massive planets, water exists as a supercritical convecting fluid mixed with gas from the disk. Typically, the core <span class="hlt">mass</span> reaches a maximum (the critical <span class="hlt">mass</span>) as a function of the total <span class="hlt">mass</span> when the core is 2-5 Earth <span class="hlt">masses</span>. The critical <span class="hlt">mass</span> depends in a complicated way on pebble size, <span class="hlt">mass</span> flux, and dust opacity due to the occasional appearance of multiple core-<span class="hlt">mass</span> maxima. The core <span class="hlt">mass</span> for an atmosphere of 50% hydrogen and helium may be a more robust indicator of the onset of gas accretion. This <span class="hlt">mass</span> is typically 1-3 Earth <span class="hlt">masses</span> for pebbles that are 50% <span class="hlt">ice</span> by <span class="hlt">mass</span>, increasing with opacity and pebble flux and decreasing with pebble <span class="hlt">ice</span>/rock ratio.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790005809','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790005809"><span>Evaporation of <span class="hlt">ice</span> in planetary atmospheres: <span class="hlt">Ice</span>-covered rivers on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wallace, D.; Sagan, C.</p> <p>1978-01-01</p> <p>The evaporation rate of water <span class="hlt">ice</span> on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the <span class="hlt">ice</span> layer. The thickness of the <span class="hlt">ice</span> is governed principally by the solar flux which penetrates the <span class="hlt">ice</span> layer and then is conducted back to the surface. Evaporation from the surface is governed by wind and free convection. In the absence of wind, eddy diffusion is caused by the lower <span class="hlt">density</span> of water vapor in comparison to the <span class="hlt">density</span> of the Martian atmosphere. For mean martian insolations, the evaporation rate above the <span class="hlt">ice</span> is approximately 10 to the minus 8th power gm/sq cm/s. Evaporation rates are calculated for a wide range of frictional velocities, atmospheric pressures, and insolations and it seems clear that at least some subset of observed Martian channels may have formed as <span class="hlt">ice</span>-chocked rivers. Typical equilibrium thicknesses of such <span class="hlt">ice</span> covers are approximately 10m to 30 m; typical surface temperatures are 210 to 235 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712799K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712799K"><span>Characterization of signatures from organic compounds in CDA <span class="hlt">mass</span> spectra of <span class="hlt">ice</span> particles in Saturn's E-ring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khawaja, Nozair; Postberg, Frank; Reviol, Rene; Srama, Ralf</p> <p>2015-04-01</p> <p>The major source of <span class="hlt">ice</span> particles in Saturn's E-ring is Enceladus - a geological active moon of Saturn. Enceladus is emanating <span class="hlt">ice</span> particles from its fractured south polar terrain (SPT), the so-called "Tiger Stripes". The source of Enceladus activity and many of the <span class="hlt">ice</span> particles is a subsurface ocean. The Cosmic Dust Analyzer (CDA) onboard the Cassini spacecraft is sampling these icy particles and producing TOF <span class="hlt">mass</span> spectra of cations of impinging particles [1]. Three compositional types of <span class="hlt">ice</span> particles have been identified from CDA-<span class="hlt">mass</span> spectra: (i) pure water <span class="hlt">ice</span> (Type-1) (ii) organic rich (Type-2) (iii) salt rich (Type-3) [2][3]. These organic rich (Type-2) spectra are particularly abundant in the icy jets of Enceladus as we found out during the Cassini's Enceladus flybys (E17 and E18) in 2012 [4]. We present a compositional analysis of the CDA spectra of these organic rich icy grains sampled in the E ring. We have characterized hundreds of Type-2 spectra of impinging <span class="hlt">ice</span> particles. These were recorded at different impact velocities causing different molecular fragmentation patterns observed in the <span class="hlt">mass</span> spectra. We defined 3 typical impact speed intervals: (i) 4-7 km/s (ii) 8-11 km/s and (iii) 12-16km/s. Organic features best observed at slow (4-7 km/s) or at intermediate (8-11 km/s) impact velocity ranges. Several classes of organic rich spectra are identified. Classifying Type-2 spectra are according to their characteristic <span class="hlt">mass</span> lines of possible organic species. We try to infer the composition of each class of organic rich spectra is inferred by using an experimental setup (IR-FL-MALDI) to simulate the CDA spectra of different compositional types. In the laboratory we have used infrared laser to disperse a micro-beam of a water solution [5]. The laser energy is adjusted to simulate different impact velocities of <span class="hlt">ice</span> particles on the CDA. Four families of organic compounds including alcohols, fatty acids, amines and aromatic, with varying number of carbon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C54A..03L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C54A..03L"><span>Inferring unknow boundary conditions of the Greenland <span class="hlt">Ice</span> Sheet by assimilating ICESat-1 and <span class="hlt">Ice</span>Bridge altimetry intothe <span class="hlt">Ice</span> Sheet System Model.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Larour, E. Y.; Khazendar, A.; Seroussi, H. L.; Schlegel, N.; Csatho, B. M.; Schenk, A. F.; Rignot, E. J.; Morlighem, M.</p> <p>2014-12-01</p> <p>Altimetry signals from missions such as ICESat-1, CryoSat, EnviSat, as well as altimeters onboard Operation <span class="hlt">Ice</span>Bridge provide vital insights into processes such as surface <span class="hlt">mass</span> balance, <span class="hlt">mass</span> transport and <span class="hlt">ice</span>-flow dynamics. Historically however, <span class="hlt">ice</span>-flow models have been focused on assimilating surface velocities from satellite-based radar observations, to infer properties such as basal friction or the position of the bedrock. Here, we leverage a new methodology based on automatic differentation of the <span class="hlt">Ice</span> Sheet System Model to assimilate surface altimetry data into a reconstruction of the past decade of <span class="hlt">ice</span> flow on the North Greenland area. We infer corrections to boundary conditions such as basal friction and surface <span class="hlt">mass</span> balance, as well as corrections to the <span class="hlt">ice</span> hardness, to best-match the observed altimetry record. We compare these corrections between glaciers such as Petermann Glacier, 79 North and Zacchariae Isstrom. The altimetry signals exhibit very different patterns between East and West, which translate into very different signatures for the inverted boundary conditions. This study gives us greater insights into what differentiates different basins, both in terms of <span class="hlt">mass</span> transport and <span class="hlt">ice</span>-flow dynamics, and what could bethe controlling mechanisms behind the very different evolutions of these basins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C22A..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C22A..06R"><span>Spatiotemporal Variability of Meltwater Refreezing in Southwest Greenland <span class="hlt">Ice</span> Sheet Firn</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rennermalm, A. K.; Hock, R.; Tedesco, M.; Corti, G.; Covi, F.; Miège, C.; Kingslake, J.; Leidman, S. Z.; Munsell, S.</p> <p>2017-12-01</p> <p>A substantial fraction of the summer meltwater formed on the surface of the Greenland <span class="hlt">ice</span> sheet is retained in firn, while the remaining portion runs to the ocean through surface and subsurface channels. Refreezing of meltwater in firn can create impenetrable <span class="hlt">ice</span> lenses, hence being a crucial process in the redistribution of surface runoff. To quantify the impact of refreezing on runoff and current and future Greenland surface <span class="hlt">mass</span> balance, a three year National Science Foundation funded project titled "Refreezing in the firn of the Greenland <span class="hlt">ice</span> sheet: Spatiotemporal variability and implications for <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance" started this past year. Here we present an overview of the project and some initial results from the first field season in May 2017 conducted in proximity of the DYE-2 site in the percolation zone of the Southwest Greenland <span class="hlt">ice</span> sheet at elevations between 1963 and 2355 m a.s.l.. During this fieldwork two automatic weather stations were deployed, outfitted with surface energy balance sensors and 16 m long thermistor strings, over 300 km of ground penetrating radar data were collected, and five 20-26 m deep firn cores were extracted and analyzed for <span class="hlt">density</span> and stratigraphy. Winter snow accumulation was measured along the radar tracks. Preliminary work on the firn-core data reveals increasing frequency and thickness of <span class="hlt">ice</span> lenses at lower <span class="hlt">ice</span>-sheet elevations, in agreement with other recent work in the area. Data collected within this project will facilitate advances in our understanding of the spatiotemporal variability of firn refreezing and its role in the hydrology and surface <span class="hlt">mass</span> balance of the Greenland <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IJMPB..3150237M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IJMPB..3150237M"><span>Phase transition and monopole <span class="hlt">densities</span> in a nearest neighbor two-dimensional spin <span class="hlt">ice</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morais, C. W.; de Freitas, D. N.; Mota, A. L.; Bastone, E. C.</p> <p>2017-12-01</p> <p>In this work, we show that, due to the alternating orientation of the spins in the ground state of the artificial square spin <span class="hlt">ice</span>, the influence of a set of spins at a certain distance of a reference spin decreases faster than the expected result for the long range dipolar interaction, justifying the use of the nearest neighbor two-dimensional square spin <span class="hlt">ice</span> model as an effective model. Using an extension of the model presented in Y. L. Xie et al., Sci. Rep. 5, 15875 (2015), considering the influence of the eight nearest neighbors of each spin on the lattice, we analyze the thermodynamics of the model and study the dependence of monopoles and string <span class="hlt">densities</span> as a function of the temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=46606','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=46606"><span>Galaxy dynamics and the <span class="hlt">mass</span> <span class="hlt">density</span> of the universe.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rubin, V C</p> <p>1993-01-01</p> <p>Dynamical evidence accumulated over the past 20 years has convinced astronomers that luminous matter in a spiral galaxy constitutes no more than 10% of the <span class="hlt">mass</span> of a galaxy. An additional 90% is inferred by its gravitational effect on luminous material. Here I review recent observations concerning the distribution of luminous and nonluminous matter in the Milky Way, in galaxies, and in galaxy clusters. Observations of neutral hydrogen disks, some extending in radius several times the optical disk, confirm that a massive dark halo is a major component of virtually every spiral. A recent surprise has been the discovery that stellar and gas motions in ellipticals are enormously complex. To date, only for a few spheroidal galaxies do the velocities extend far enough to probe the outer <span class="hlt">mass</span> distribution. But the diverse kinematics of inner cores, peripheral to deducing the overall <span class="hlt">mass</span> distribution, offer additional evidence that ellipticals have acquired gas-rich systems after initial formation. Dynamical results are consistent with a low-<span class="hlt">density</span> universe, in which the required dark matter could be baryonic. On smallest scales of galaxies [10 kiloparsec (kpc); Ho = 50 km.sec-1.megaparsec-1] the luminous matter constitutes only 1% of the closure <span class="hlt">density</span>. On scales greater than binary galaxies (i.e., >/=100 kpc) all systems indicate a <span class="hlt">density</span> approximately 10% of the closure <span class="hlt">density</span>, a <span class="hlt">density</span> consistent with the low baryon <span class="hlt">density</span> in the universe. If large-scale motions in the universe require a higher <span class="hlt">mass</span> <span class="hlt">density</span>, these motions would constitute the first dynamical evidence for nonbaryonic matter in a universe of higher <span class="hlt">density</span>. Images Fig. 3 Fig. 5 PMID:11607393</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006602','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006602"><span>Dynamic Inland Propagation of Thinning Due to <span class="hlt">Ice</span> Loss at the Margins of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wang, Wei Li; Li, Jun J.; Zwally, H. Jay</p> <p>2012-01-01</p> <p><span class="hlt">Mass</span>-balance analysis of the Greenland <span class="hlt">ice</span> sheet based on surface elevation changes observed by the European Remote-sensing Satellite (ERS) (1992-2002) and <span class="hlt">Ice</span>, Cloud and land Elevation Satellite (ICESat) (2003-07) indicates that the strongly increased <span class="hlt">mass</span> loss at lower elevations (<2000 m) of the <span class="hlt">ice</span> sheet, as observed during 2003-07, appears to induce interior <span class="hlt">ice</span> thinning at higher elevations. In this paper, we perform a perturbation experiment with a three-dimensional anisotropic <span class="hlt">ice</span>-flow model (AIF model) to investigate this upstream propagation. Observed thinning rates in the regions below 2000m elevation are used as perturbation inputs. The model runs with perturbation for 10 years show that the extensive <span class="hlt">mass</span> loss at the <span class="hlt">ice</span>-sheet margins does in fact cause interior thinning on short timescales (i.e. decadal). The modeled pattern of thinning over the <span class="hlt">ice</span> sheet agrees with the observations, which implies that the strong <span class="hlt">mass</span> loss since the early 2000s at low elevations has had a dynamic impact on the entire <span class="hlt">ice</span> sheet. The modeling results also suggest that even if the large <span class="hlt">mass</span> loss at the margins stopped, the interior <span class="hlt">ice</span> sheet would continue thinning for 300 years and would take thousands of years for full dynamic recovery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACPD...13.4331J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACPD...13.4331J"><span>On the relationship between Arctic <span class="hlt">ice</span> clouds and polluted air <span class="hlt">masses</span> over the north slope of Alaska in April 2008</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jouan, C.; Pelon, J.; Girard, E.; Ancellet, G.; Blanchet, J. P.; Delanoë, J.</p> <p>2013-02-01</p> <p>Recently, two Types of <span class="hlt">Ice</span> Clouds (TICs) properties have been characterized using ISDAC airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (<10 L-1) and larger (>110 μm) <span class="hlt">ice</span> crystals, a larger <span class="hlt">ice</span> supersaturation (>15%) and a fewer <span class="hlt">ice</span> nuclei (IN) concentration (<2 order of magnitude) when compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the <span class="hlt">ice</span> nucleating properties of IN through acidification, resulting to a smaller concentration of larger <span class="hlt">ice</span> crystals and leading to precipitation (e.g. cloud regime TIC-2B) because of the reduced competition for the same available moisture. Here, the origin of air <span class="hlt">masses</span> forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air <span class="hlt">masses</span> transport from the three potentials SO2 emission areas to Alaska: eastern China and Siberia where anthropogenic and biomass burning emission respectively are produced and the volcanic region from the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China/Siberia over Alaska, most probably with the contribution of acid volcanic aerosol during the TIC-2B period. OMI observations reveal that SO2 concentrations in air <span class="hlt">masses</span> forming the TIC-2B were larger than in air <span class="hlt">masses</span> forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results strongly support the hypothesis that acidic coating on IN are at the origin of the formation of TIC-2B.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850017730&hterms=Parkinsons+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DParkinsons%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850017730&hterms=Parkinsons+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DParkinsons%2Bcirculation"><span>Possible Sea <span class="hlt">Ice</span> Impacts on Oceanic Deep Convection</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, C. L.</p> <p>1984-01-01</p> <p>Many regions of the world ocean known or suspected to have deep convection are sea-<span class="hlt">ice</span> covered for at least a portion of the annual cycle. As this suggests that sea <span class="hlt">ice</span> might have some impact on generating or maintaining this phenomenon, several mechanisms by which sea <span class="hlt">ice</span> could exert an influence are presented in the following paragraphs. Sea <span class="hlt">ice</span> formation could be a direct causal factor in deep convection by providing the surface <span class="hlt">density</span> increase necessary to initiate the convective overturning. As sea <span class="hlt">ice</span> forms, either by <span class="hlt">ice</span> accretion or by in situ <span class="hlt">ice</span> formation in open water or in lead areas between <span class="hlt">ice</span> floes, salt is rejected to the underlying water. This increases the water salinity, thereby increasing water <span class="hlt">density</span> in the mixed layer under the <span class="hlt">ice</span>. A sufficient increase in <span class="hlt">density</span> will lead to mixing with deeper waters, and perhaps to deep convection or even bottom water formation. Observations are needed to establish whether this process is actually occurring; it is most likely in regions with extensive <span class="hlt">ice</span> formation and a relatively unstable oceanic <span class="hlt">density</span> structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C44A..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C44A..02B"><span>connecting the dots between Greenland <span class="hlt">ice</span> sheet surface melting and <span class="hlt">ice</span> flow dynamics (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Box, J. E.; Colgan, W. T.; Fettweis, X.; Phillips, T. P.; Stober, M.</p> <p>2013-12-01</p> <p>This presentation is of a 'unified theory' in glaciology that first identifies surface albedo as a key factor explaining total <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance and then surveys a mechanistic self-reinforcing interaction between melt water and <span class="hlt">ice</span> flow dynamics. The theory is applied in a near-real time total Greenland <span class="hlt">mass</span> balance retrieval based on surface albedo, a powerful integrator of the competing effects of accumulation and ablation. New snowfall reduces sunlight absorption and increases meltwater retention. Melting amplifies absorbed sunlight through thermal metamorphism and bare <span class="hlt">ice</span> expansion in space and time. By ';following the melt'; we reveal mechanisms linking existing science into a unified theory. Increasing meltwater softens the <span class="hlt">ice</span> sheet in three ways: 1.) sensible heating given the water temperature exceeds that of the <span class="hlt">ice</span> sheet interior; 2.) Some infiltrating water refreezes, transferring latent heat to the <span class="hlt">ice</span>; 3.) Friction from water turbulence heats the <span class="hlt">ice</span>. It has been shown that for a point on the <span class="hlt">ice</span> sheet, basal lubrication increases <span class="hlt">ice</span> flow speed to a time when an efficient sub-glacial drainage network develops that reduces this effect. Yet, with an increasing melt duration the point where the <span class="hlt">ice</span> sheet glides on a wet bed increases inland to a larger area. This effect draws down the <span class="hlt">ice</span> surface elevation, contributing to the ';elevation feedback'. In a perpetual warming scenario, the elevation feedback ultimately leads to <span class="hlt">ice</span> sheet loss reversible only through much slower <span class="hlt">ice</span> sheet growth in an <span class="hlt">ice</span> age environment. As the inland <span class="hlt">ice</span> sheet accelerates, the horizontal extension pulls cracks and crevasses open, trapping more sunlight, amplifying the effect of melt accelerated <span class="hlt">ice</span>. As the bare <span class="hlt">ice</span> area increases, the direct sun-exposed crevassed and infiltration area increases further allowing the <span class="hlt">ice</span> warming process to occur more broadly. Considering hydrofracture [a.k.a. hydrofracking]; surface meltwater fills cracks, attacking the <span class="hlt">ice</span> integrity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53C0799H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53C0799H"><span>Validation of Modelled <span class="hlt">Ice</span> Dynamics of the Greenland <span class="hlt">Ice</span> Sheet using Historical Forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoffman, M. J.; Price, S. F.; Howat, I. M.; Bonin, J. A.; Chambers, D. P.; Tezaur, I.; Kennedy, J. H.; Lenaerts, J.; Lipscomb, W. H.; Neumann, T.; Nowicki, S.; Perego, M.; Saba, J. L.; Salinger, A.; Guerber, J. R.</p> <p>2015-12-01</p> <p>Although <span class="hlt">ice</span> sheet models are used for sea level rise projections, the degree to which these models have been validated by observations is fairly limited, due in part to the limited duration of the satellite observation era and the long adjustment time scales of <span class="hlt">ice</span> sheets. Here we describe a validation framework for the Greenland <span class="hlt">Ice</span> Sheet applied to the Community <span class="hlt">Ice</span> Sheet Model by forcing the model annually with flux anomalies at the major outlet glaciers (Enderlin et al., 2014, observed from Landsat/ASTER/Operation <span class="hlt">Ice</span>Bridge) and surface <span class="hlt">mass</span> balance (van Angelen et al., 2013, calculated from RACMO2) for the period 1991-2012. The <span class="hlt">ice</span> sheet model output is compared to <span class="hlt">ice</span> surface elevation observations from ICESat and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> change observations from GRACE. Early results show promise for assessing the performance of different model configurations. Additionally, we explore the effect of <span class="hlt">ice</span> sheet model resolution on validation skill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..4411463S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..4411463S"><span>Algae Drive Enhanced Darkening of Bare <span class="hlt">Ice</span> on the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stibal, Marek; Box, Jason E.; Cameron, Karen A.; Langen, Peter L.; Yallop, Marian L.; Mottram, Ruth H.; Khan, Alia L.; Molotch, Noah P.; Chrismas, Nathan A. M.; Calı Quaglia, Filippo; Remias, Daniel; Smeets, C. J. P. Paul; van den Broeke, Michiel R.; Ryan, Jonathan C.; Hubbard, Alun; Tranter, Martyn; van As, Dirk; Ahlstrøm, Andreas P.</p> <p>2017-11-01</p> <p>Surface ablation of the Greenland <span class="hlt">ice</span> sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the <span class="hlt">ice</span> sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the <span class="hlt">ice</span> sheet. The impact of algae on bare <span class="hlt">ice</span> darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare <span class="hlt">ice</span> darkening, and incorporating the algal darkening effect will improve <span class="hlt">mass</span> balance and sea level projections of the Greenland <span class="hlt">ice</span> sheet and <span class="hlt">ice</span> <span class="hlt">masses</span> elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P43C2117H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P43C2117H"><span><span class="hlt">Ice</span> under cover: Using bulk spatial and physical properties of probable ground <span class="hlt">ice</span> driven <span class="hlt">mass</span> wasting features on Ceres to better understand its surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hughson, K.; Russell, C.; Schmidt, B. E.; Chilton, H.; Scully, J. E. C.; Castillo, J. C.; Combe, J. P.; Ammannito, E.; Sizemore, H.; Platz, T.; Byrne, S.; Nathues, A.; Raymond, C. A.</p> <p>2016-12-01</p> <p>NASA's Dawn spacecraft arrived at Ceres on March 6, 2015, and has been studying the dwarf planet through a series of successively lower orbits, obtaining morphological and topographical image, mineralogical, elemental composition, and gravity data (Russell et al., 2016). Images taken by Dawn's Framing Camera show a multitude of flow features that were broadly interpreted as ground <span class="hlt">ice</span> related structures either similar to <span class="hlt">ice</span> cored/<span class="hlt">ice</span> cemented flows (as seen on Earth and Mars), long run-out landslides, or fluidized ejecta (as seen on Mars) by Schmidt et al. (2016a and 2016b) and Buczkowski et al. (2016). The aforementioned <span class="hlt">ice</span> cored/<span class="hlt">ice</span> cemented-like flows are present only at high latitudes. Results from Dawn's Gamma Ray and Neutron Detector (GRaND) indicate a shallow <span class="hlt">ice</span> table on Ceres above 45-50°N/S, which supports the interpretation that these flows are <span class="hlt">ice</span>-rich (Prettyman et al., 2016). A near coincident spectral detection of H2O <span class="hlt">ice</span> with one of these <span class="hlt">ice</span> cored/<span class="hlt">ice</span> cemented-like flows in Oxo crater by Dawn's Visual and Infrared spectrometer (VIR) further bolsters this claim (Combe et al., 2016). We use aggregate spatial and physical properties of these <span class="hlt">ice</span> attributed cerean flows, such as flow orientation, inclination, preference for north or south facing slopes, drop height to run-out length ratio, geographical location, and areal number <span class="hlt">density</span> to better understand the rheology and distribution of ground <span class="hlt">ice</span> in Ceres' uppermost layer. By combining these data with local spectroscopic, global elemental abundance, experimentally derived physical properties of cerean analogue material, and other morphological information (such as the morphologies of flow hosting craters) we intend to further test the ground <span class="hlt">ice</span> hypothesis for the formation of these flows and constrain the global distribution of near surface ground <span class="hlt">ice</span> on Ceres to a higher fidelity than what would be possible using GRaND and VIR observations alone. References: Buczkowski et al., (2016) Science</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.A13D0966Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.A13D0966Y"><span>Seasonal origins of air <span class="hlt">masses</span> transported to Mount Wrangell, Alaska, and comparison with the past atmospheric dust and tritium variations in its <span class="hlt">ice</span> core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yasunari, T. J.; Shiraiwa, T.; Kanamori, S.; Fujii, Y.; Igarashi, M.; Yamazaki, K.; Benson, C. S.; Hondoh, T.</p> <p>2006-12-01</p> <p>The North Pacific region is subject to various climatic phenomena such as the Pacific Decadal Oscillation (PDO), the El Niño-Southern Oscillation (ENSO), and the Arctic Oscillation (AO), significantly affecting the ocean and the atmosphere. Additionally, material circulation is also very active in this region such as spring dust storms in the desert and arid regions of East Asia and forest fires in Siberia and Alaska. Understanding the complex connections among the climatic phenomena and the material circulation would help in attempts to predict future climate changes. For this subject, we drilled a 50-m <span class="hlt">ice</span> core at the summit of Mount Wrangell, which is located near the coast of Alaska (62°162'170"162°171'N, 144°162'170"162;°171'W, and 4100-m). We analyzed dust particle number <span class="hlt">density</span>, tritium concentration, and 171 171 171 171 170 162 171 D in the core. The <span class="hlt">ice</span> core spanned the years from 1992 to 2002 and we finally divided the years into five parts (early-spring; late-spring; summer; fall; winter). Dust and tritium amounts varied annually and intra-annually. For further understanding of the factors on those variations, we should know the origins of the seasonal dust and tritium. Hence, we examined their origins by the calculation of everyday 10-days backward trajectory analysis from January 1992 to August 2002 with 3-D wind data of the European Center for Medium-Range Weather Forecast (ECMWF). In early spring, the air <span class="hlt">mass</span> from East Asia increased and it also explained dust increases in springtime, although the air contribution in winter increased too. In late spring, the air <span class="hlt">mass</span> from the stratosphere increased, and it also corresponded to the stratospheric tritium increase in the <span class="hlt">ice</span> core. The air <span class="hlt">masses</span> from Siberia and the North Pacific in the mid-latitude always significantly contributed to Mount Wrangell, although those maximum contributions were fall and summer, respectively. The air <span class="hlt">mass</span> originating in the interior of Alaska and North America did</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917148O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917148O"><span>Water <span class="hlt">ice</span> cloud property retrievals at Mars with OMEGA:Spatial distribution and column <span class="hlt">mass</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olsen, Kevin S.; Madeleine, Jean-Baptiste; Szantai, Andre; Audouard, Joachim; Geminale, Anna; Altieri, Francesca; Bellucci, Giancarlo; Montabone, Luca; Wolff, Michael J.; Forget, Francois</p> <p>2017-04-01</p> <p>Spectral images of Mars recorded by OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) on Mars Express can be used to deduce the mean effective radius (r_eff) and optical depth (τ_i) of water <span class="hlt">ice</span> particles in clouds. Using new data sets for a priori surface temperature, vertical profiles of atmospheric temperature, dust opacity, and multi-spectral surface albedo, we have analyzed over 40 OMEGA image cubes over the Tharsis, Arabia, and Syrtis Major quadrangles, and mapped the spatial distribution of r_eff, τ_i, and water <span class="hlt">ice</span> column <span class="hlt">mass</span>. We also explored the parameter space of r_eff and τ_i, which are inversely proportional, and the <span class="hlt">ice</span> cloud index (ICI), which is the ratio of the reflectance at 3.4 and 3.52 μm, and indicates the thickness of water <span class="hlt">ice</span> clouds. We found that the ICI, trivial to calculate for OMEGA image cubes, can be a proxy for column <span class="hlt">mass</span>, which is very expensive to compute, requiring accurate retrievals of surface albedo, r_eff, and τ_i. Observing the spatial distribution, we find that within each cloud system, r_eff varies about a mean of 2.1 μm, that τi is closely related to r_eff, and that the values allowed for τ_i, given r_eff, are related to the ICI. We also observe areas where our retrieval detects very thin clouds made of very large particles (mean of 12.5 μm), which are still under investigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10.2361N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10.2361N"><span>A daily, 1 km resolution data set of downscaled Greenland <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> balance (1958-2015)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; Lhermitte, Stef; Howat, Ian; Fettweis, Xavier; van den Broeke, Michiel R.</p> <p>2016-10-01</p> <p>This study presents a data set of daily, 1 km resolution Greenland <span class="hlt">ice</span> sheet (GrIS) surface <span class="hlt">mass</span> balance (SMB) covering the period 1958-2015. Applying corrections for elevation, bare <span class="hlt">ice</span> albedo and accumulation bias, the high-resolution product is statistically downscaled from the native daily output of the polar regional climate model RACMO2.3 at 11 km. The data set includes all individual SMB components projected to a down-sampled version of the Greenland <span class="hlt">Ice</span> Mapping Project (GIMP) digital elevation model and <span class="hlt">ice</span> mask. The 1 km mask better resolves narrow ablation zones, valley glaciers, fjords and disconnected <span class="hlt">ice</span> caps. Relative to the 11 km product, the more detailed representation of isolated glaciated areas leads to increased precipitation over the southeastern GrIS. In addition, the downscaled product shows a significant increase in runoff owing to better resolved low-lying marginal glaciated regions. The combined corrections for elevation and bare <span class="hlt">ice</span> albedo markedly improve model agreement with a newly compiled data set of ablation measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5489271','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5489271"><span>Decreasing cloud cover drives the recent <span class="hlt">mass</span> loss on the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hofer, Stefan; Tedstone, Andrew J.; Fettweis, Xavier; Bamber, Jonathan L.</p> <p>2017-01-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been losing <span class="hlt">mass</span> at an accelerating rate since the mid-1990s. This has been due to both increased <span class="hlt">ice</span> discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface <span class="hlt">mass</span> balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface <span class="hlt">mass</span> loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation. PMID:28782014</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28782014','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28782014"><span>Decreasing cloud cover drives the recent <span class="hlt">mass</span> loss on the Greenland <span class="hlt">Ice</span> Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hofer, Stefan; Tedstone, Andrew J; Fettweis, Xavier; Bamber, Jonathan L</p> <p>2017-06-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) has been losing <span class="hlt">mass</span> at an accelerating rate since the mid-1990s. This has been due to both increased <span class="hlt">ice</span> discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface <span class="hlt">mass</span> balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface <span class="hlt">mass</span> loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A13E2121S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A13E2121S"><span>Impacts of a Stochastic <span class="hlt">Ice</span> <span class="hlt">Mass</span>-Size Relationship on Squall Line Ensemble Simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stanford, M.; Varble, A.; Morrison, H.; Grabowski, W.; McFarquhar, G. M.; Wu, W.</p> <p>2017-12-01</p> <p>Cloud and precipitation structure, evolution, and cloud radiative forcing of simulated mesoscale convective systems (MCSs) are significantly impacted by <span class="hlt">ice</span> microphysics parameterizations. Most microphysics schemes assume power law relationships with constant parameters for <span class="hlt">ice</span> particle <span class="hlt">mass</span>, area, and terminal fallspeed relationships as a function of size, despite observations showing that these relationships vary in both time and space. To account for such natural variability, a stochastic representation of <span class="hlt">ice</span> microphysical parameters was developed using the Predicted Particle Properties (P3) microphysics scheme in the Weather Research and Forecasting model, guided by in situ aircraft measurements from a number of field campaigns. Here, the stochastic framework is applied to the "a" and "b" parameters of the unrimed <span class="hlt">ice</span> <span class="hlt">mass</span>-size (m-D) relationship (m=aDb) with co-varying "a" and "b" values constrained by observational distributions tested over a range of spatiotemporal autocorrelation scales. Diagnostically altering a-b pairs in three-dimensional (3D) simulations of the 20 May 2011 Midlatitude Continental Convective Clouds Experiment (MC3E) squall line suggests that these parameters impact many important characteristics of the simulated squall line, including reflectivity structure (particularly in the anvil region), surface rain rates, surface and top of atmosphere radiative fluxes, buoyancy and latent cooling distributions, and system propagation speed. The stochastic a-b P3 scheme is tested using two frameworks: (1) a large ensemble of two-dimensional idealized squall line simulations and (2) a smaller ensemble of 3D simulations of the 20 May 2011 squall line, for which simulations are evaluated using observed radar reflectivity and radial velocity at multiple wavelengths, surface meteorology, and surface and satellite measured longwave and shortwave radiative fluxes. Ensemble spreads are characterized and compared against initial condition ensemble spreads</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22679712-steamworlds-atmospheric-structure-critical-mass-planets-accreting-icy-pebbles','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22679712-steamworlds-atmospheric-structure-critical-mass-planets-accreting-icy-pebbles"><span>Steamworlds: Atmospheric Structure and Critical <span class="hlt">Mass</span> of Planets Accreting Icy Pebbles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chambers, John, E-mail: jchambers@carnegiescience.edu</p> <p></p> <p>In the core accretion model, gas-giant planets first form a solid core, which then accretes gas from a protoplanetary disk when the core exceeds a critical <span class="hlt">mass</span>. Here, we model the atmosphere of a core that grows by accreting <span class="hlt">ice</span>-rich pebbles. The <span class="hlt">ice</span> fraction of pebbles evaporates in warm regions of the atmosphere, saturating it with water vapor. Excess water precipitates to lower altitudes. Beneath an outer radiative region, the atmosphere is convective, following a moist adiabat in saturated regions due to water condensation and precipitation. Atmospheric <span class="hlt">mass</span>, <span class="hlt">density</span>, and temperature increase with core <span class="hlt">mass</span>. For nominal model parameters, planetsmore » with core <span class="hlt">masses</span> (<span class="hlt">ice</span> + rock) between 0.08 and 0.16 Earth <span class="hlt">masses</span> have surface temperatures between 273 and 647 K and form an ocean. In more massive planets, water exists as a supercritical convecting fluid mixed with gas from the disk. Typically, the core <span class="hlt">mass</span> reaches a maximum (the critical <span class="hlt">mass</span>) as a function of the total <span class="hlt">mass</span> when the core is 2–5 Earth <span class="hlt">masses</span>. The critical <span class="hlt">mass</span> depends in a complicated way on pebble size, <span class="hlt">mass</span> flux, and dust opacity due to the occasional appearance of multiple core-<span class="hlt">mass</span> maxima. The core <span class="hlt">mass</span> for an atmosphere of 50% hydrogen and helium may be a more robust indicator of the onset of gas accretion. This <span class="hlt">mass</span> is typically 1–3 Earth <span class="hlt">masses</span> for pebbles that are 50% <span class="hlt">ice</span> by <span class="hlt">mass</span>, increasing with opacity and pebble flux and decreasing with pebble <span class="hlt">ice</span>/rock ratio.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16552103','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16552103"><span>Computation of <span class="hlt">mass-density</span> images from x-ray refraction-angle images.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wernick, Miles N; Yang, Yongyi; Mondal, Indrasis; Chapman, Dean; Hasnah, Moumen; Parham, Christopher; Pisano, Etta; Zhong, Zhong</p> <p>2006-04-07</p> <p>In this paper, we investigate the possibility of computing quantitatively accurate images of <span class="hlt">mass</span> <span class="hlt">density</span> variations in soft tissue. This is a challenging task, because <span class="hlt">density</span> variations in soft tissue, such as the breast, can be very subtle. Beginning from an image of refraction angle created by either diffraction-enhanced imaging (DEI) or multiple-image radiography (MIR), we estimate the <span class="hlt">mass-density</span> image using a constrained least squares (CLS) method. The CLS algorithm yields accurate <span class="hlt">density</span> estimates while effectively suppressing noise. Our method improves on an analytical method proposed by Hasnah et al (2005 Med. Phys. 32 549-52), which can produce significant artefacts when even a modest level of noise is present. We present a quantitative evaluation study to determine the accuracy with which <span class="hlt">mass</span> <span class="hlt">density</span> can be determined in the presence of noise. Based on computer simulations, we find that the <span class="hlt">mass-density</span> estimation error can be as low as a few per cent for typical <span class="hlt">density</span> variations found in the breast. Example images computed from less-noisy real data are also shown to illustrate the feasibility of the technique. We anticipate that <span class="hlt">density</span> imaging may have application in assessment of water content of cartilage resulting from osteoarthritis, in evaluation of bone <span class="hlt">density</span>, and in mammographic interpretation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=gas+AND+liquid&pg=5&id=EJ832497','ERIC'); return false;" href="https://eric.ed.gov/?q=gas+AND+liquid&pg=5&id=EJ832497"><span>Small-Scale Production of High-<span class="hlt">Density</span> Dry <span class="hlt">Ice</span>: A Variant Combination of Two Classic Demonstrations</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Flowers, Paul A.</p> <p>2009-01-01</p> <p>Easily recoverable, thumb-sized pieces of high-<span class="hlt">density</span> dry <span class="hlt">ice</span> are conveniently produced by deposition of carbon dioxide within a test tube submerged in liquid nitrogen. A carbon dioxide-filled balloon sealed over the mouth of the test tube serves as a gas reservoir, and further permits a dramatic demonstration of both the gas-to-solid phase…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JCAP...04..007L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JCAP...04..007L"><span>The maximal-<span class="hlt">density</span> <span class="hlt">mass</span> function for primordial black hole dark matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lehmann, Benjamin V.; Profumo, Stefano; Yant, Jackson</p> <p>2018-04-01</p> <p>The advent of gravitational wave astronomy has rekindled interest in primordial black holes (PBH) as a dark matter candidate. As there are many different observational probes of the PBH <span class="hlt">density</span> across different <span class="hlt">masses</span>, constraints on PBH models are dependent on the functional form of the PBH <span class="hlt">mass</span> function. This complicates general statements about the <span class="hlt">mass</span> functions allowed by current data, and, in particular, about the maximum total <span class="hlt">density</span> of PBH. Numerical studies suggest that some forms of extended <span class="hlt">mass</span> functions face tighter constraints than monochromatic <span class="hlt">mass</span> functions, but they do not preclude the existence of a functional form for which constraints are relaxed. We use analytical arguments to show that the <span class="hlt">mass</span> function which maximizes the fraction of the matter <span class="hlt">density</span> in PBH subject to all constraints is a finite linear combination of monochromatic <span class="hlt">mass</span> functions. We explicitly compute the maximum fraction of dark matter in PBH for different combinations of current constraints, allowing for total freedom of the <span class="hlt">mass</span> function. Our framework elucidates the dependence of the maximum PBH <span class="hlt">density</span> on the form of observational constraints, and we discuss the implications of current and future constraints for the viability of the PBH dark matter paradigm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P43E..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P43E..01H"><span>The <span class="hlt">Mass</span> of Saturn's B ring from hidden <span class="hlt">density</span> waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hedman, M. M.; Nicholson, P. D.</p> <p>2015-12-01</p> <p>The B ring is Saturn's brightest and most opaque ring, but many of its fundamental parameters, including its total <span class="hlt">mass</span>, are not well constrained. Elsewhere in the rings, the best <span class="hlt">mass</span> <span class="hlt">density</span> estimates come from spiral waves driven by mean-motion resonances with Saturn's various moons, but such waves have been hard to find in the B ring. We have developed a new wavelet-based technique, for combining data from multiple stellar occultations that allows us to isolate the <span class="hlt">density</span> wave signals from other ring structures. This method has been applied to 5 <span class="hlt">density</span> waves using 17 occultations of the star gamma Crucis observed by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. Two of these waves (generated by the Janus 2:1 and Mimas 5:2 Inner Lindblad Resonances) are visible in individual occultation profiles, but the other three wave signatures ( associated with the Janus 3:2, Enceladus 3:1 and Pandora 3:2 Inner Lindblad Resonances ) are not visible in individual profiles and can only be detected in the combined dataset. Estimates of the ring's surface <span class="hlt">mass</span> <span class="hlt">density</span> derived from these five waves fall between 40 and 140 g/cm^2. Surprisingly, these <span class="hlt">mass</span> <span class="hlt">density</span> estimates show no obvious correlation with the ring's optical depth. Furthermore, these data indicate that the total <span class="hlt">mass</span> of the B ring is probably between one-third and two-thirds the <span class="hlt">mass</span> of Saturn's moon Mimas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9538W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9538W"><span>Small scale variability of snow properties on Antarctic sea <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wever, Nander; Leonard, Katherine; Paul, Stephan; Jacobi, Hans-Werner; Proksch, Martin; Lehning, Michael</p> <p>2016-04-01</p> <p>Snow on sea <span class="hlt">ice</span> plays an important role in air-<span class="hlt">ice</span>-sea interactions, as snow accumulation may for example increase the albedo. Snow is also able to smooth the <span class="hlt">ice</span> surface, thereby reducing the surface roughness, while at the same time it may generate new roughness elements by interactions with the wind. Snow <span class="hlt">density</span> is a key property in many processes, for example by influencing the thermal conductivity of the snow layer, radiative transfer inside the snow as well as the effects of aerodynamic forcing on the snowpack. By comparing snow <span class="hlt">density</span> and grain size from snow pits and snow micro penetrometer (SMP) measurements, highly resolved <span class="hlt">density</span> and grain size profiles were acquired during two subsequent cruises of the RV Polarstern in the Weddell Sea, Antarctica, between June and October 2013. During the first cruise, SMP measurements were done along two approximately 40 m transects with a horizontal resolution of approximately 30 cm. During the second cruise, one transect was made with approximately 7.5 m resolution over a distance of 500 m. Average snow <span class="hlt">densities</span> are about 300 kg/m3, but the analysis also reveals a high spatial variability in snow <span class="hlt">density</span> on sea <span class="hlt">ice</span> in both horizontal and vertical direction, ranging from roughly 180 to 360 kg/m3. This variability is expressed by coherent snow structures over several meters. On the first cruise, the measurements were accompanied by terrestrial laser scanning (TLS) on an area of 50x50 m2. The comparison with the TLS data indicates that the spatial variability is exhibiting similar spatial patterns as deviations in surface topology. This suggests a strong influence from surface processes, for example wind, on the temporal development of <span class="hlt">density</span> or grain size profiles. The fundamental relationship between variations in snow properties, surface roughness and changes therein as investigated in this study is interpreted with respect to large-scale <span class="hlt">ice</span> movement and the <span class="hlt">mass</span> balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2655S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2655S"><span>GPS-derived estimates of surface <span class="hlt">mass</span> balance and ocean-induced basal melt for Pine Island Glacier <span class="hlt">ice</span> shelf, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shean, David E.; Christianson, Knut; Larson, Kristine M.; Ligtenberg, Stefan R. M.; Joughin, Ian R.; Smith, Ben E.; Stevens, C. Max; Bushuk, Mitchell; Holland, David M.</p> <p>2017-11-01</p> <p>In the last 2 decades, Pine Island Glacier (PIG) experienced marked speedup, thinning, and grounding-line retreat, likely due to marine <span class="hlt">ice</span>-sheet instability and <span class="hlt">ice</span>-shelf basal melt. To better understand these processes, we combined 2008-2010 and 2012-2014 GPS records with dynamic firn model output to constrain local surface and basal <span class="hlt">mass</span> balance for PIG. We used GPS interferometric reflectometry to precisely measure absolute surface elevation (zsurf) and Lagrangian surface elevation change (Dzsurf/ Dt). Observed surface elevation relative to a firn layer tracer for the initial surface (zsurf - zsurf0') is consistent with model estimates of surface <span class="hlt">mass</span> balance (SMB, primarily snow accumulation). A relatively abrupt ˜ 0.2-0.3 m surface elevation decrease, likely due to surface melt and increased compaction rates, is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed Dzsurf/ Dt trends (-1 to -4 m yr-1) for the PIG shelf sites are all highly linear. Corresponding basal melt rate estimates range from ˜ 10 to 40 m yr-1, in good agreement with those derived from <span class="hlt">ice</span>-bottom acoustic ranging, phase-sensitive <span class="hlt">ice</span>-penetrating radar, and high-resolution stereo digital elevation model (DEM) records. The GPS and DEM records document higher melt rates within and near features associated with longitudinal extension (i.e., transverse surface depressions, rifts). Basal melt rates for the 2012-2014 period show limited temporal variability despite large changes in ocean temperature recorded by moorings in Pine Island Bay. Our results demonstrate the value of long-term GPS records for <span class="hlt">ice</span>-shelf <span class="hlt">mass</span> balance studies, with implications for the sensitivity of <span class="hlt">ice</span>-ocean interaction at PIG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..12210837M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..12210837M"><span>Winter snow conditions on Arctic sea <span class="hlt">ice</span> north of Svalbard during the Norwegian young sea <span class="hlt">ICE</span> (N-<span class="hlt">ICE</span>2015) expedition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Merkouriadi, Ioanna; Gallet, Jean-Charles; Graham, Robert M.; Liston, Glen E.; Polashenski, Chris; Rösel, Anja; Gerland, Sebastian</p> <p>2017-10-01</p> <p>Snow is a crucial component of the Arctic sea <span class="hlt">ice</span> system. Its thickness and thermal properties control heat conduction and radiative fluxes across the ocean, <span class="hlt">ice</span>, and atmosphere interfaces. Hence, observations of the evolution of snow depth, <span class="hlt">density</span>, thermal conductivity, and stratigraphy are crucial for the development of detailed snow numerical models predicting energy transfer through the snow pack. Snow depth is also a major uncertainty in predicting <span class="hlt">ice</span> thickness using remote sensing algorithms. Here we examine the winter spatial and temporal evolution of snow physical properties on first-year (FYI) and second-year <span class="hlt">ice</span> (SYI) in the Atlantic sector of the Arctic Ocean, during the Norwegian young sea <span class="hlt">ICE</span> (N-<span class="hlt">ICE</span>2015) expedition (January to March 2015). During N-<span class="hlt">ICE</span>2015, the snow pack consisted of faceted grains (47%), depth hoar (28%), and wind slab (13%), indicating very different snow stratigraphy compared to what was observed in the Pacific sector of the Arctic Ocean during the SHEBA campaign (1997-1998). Average snow bulk <span class="hlt">density</span> was 345 kg m-3 and it varied with <span class="hlt">ice</span> type. Snow depth was 41 ± 19 cm in January and 56 ± 17 cm in February, which is significantly greater than earlier suggestions for this region. The snow water equivalent was 14.5 ± 5.3 cm over first-year <span class="hlt">ice</span> and 19 ± 5.4 cm over second-year <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C23C0646G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C23C0646G"><span>Numerical model of <span class="hlt">ice</span> melange expansion during abrupt <span class="hlt">ice</span>-shelf collapse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guttenberg, N.; Abbot, D. S.; Amundson, J. M.; Burton, J. C.; Cathles, L. M.; Macayeal, D. R.; Zhang, W.</p> <p>2010-12-01</p> <p>Satellite imagery of the February 2008 Wilkins <span class="hlt">Ice</span>-Shelf Collapse event reveals that a large percentage of the involved <span class="hlt">ice</span> shelf was converted to capsized icebergs and broken fragments of icebergs over a relatively short period of time, possibly less than 24 hours. The extreme violence and short time scale of the event, and the considerable reduction of gravitational potential energy between upright and capsized icebergs, suggests that iceberg capsize might be an important driving mechanism controlling both the rate and spatial extent of <span class="hlt">ice</span> shelf collapse. To investigate this suggestion, we have constructed an idealized, 2-dimensional model of a disintegrating <span class="hlt">ice</span> shelf composed of a large number (N~100 to >1000) of initially well-packed icebergs of rectangular cross section. The model geometry consists of a longitudinal cross section of the idealized <span class="hlt">ice</span> shelf from grounding line (or the upstream extent of <span class="hlt">ice</span>-shelf fragmentation) to seaward <span class="hlt">ice</span> front, and includes the region beyond the initial <span class="hlt">ice</span> front to cover the open, <span class="hlt">ice</span>-free water into which the collapsing <span class="hlt">ice</span> shelf expands. The seawater in which the icebergs float is treated as a hydrostatic fluid in the computation of iceberg orientation (e.g., the evaluation of buoyancy forces and torques), thereby eliminating the complexities of free-surface waves, but net horizontal drift of the icebergs is resisted by a linear drag law designed to energy dissipation by viscous forces and surface-gravity-wave radiation. Icebergs interact via both elastic and inelastic contacts (typically a corner of one iceberg will scrape along the face of its neighbor). <span class="hlt">Ice</span>-shelf collapse in the model is embodied by the <span class="hlt">mass</span> capsize of a large proportion of the initially packed icebergs and the consequent advancement of the <span class="hlt">ice</span> front (leading edge). Model simulations are conducted to examine (a) the threshold of stability (e.g., what <span class="hlt">density</span> of initially capsizable icebergs is needed to allow a small perturbation to the system</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P34A..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P34A..04B"><span>Slush Fund: Modeling the Multiphase Physics of Oceanic <span class="hlt">Ices</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buffo, J.; Schmidt, B. E.</p> <p>2016-12-01</p> <p>The prevalence of <span class="hlt">ice</span> interacting with an ocean, both on Earth and throughout the solar system, and its crucial role as the mediator of exchange between the hydrosphere below and atmosphere above, have made quantifying the thermodynamic, chemical, and physical properties of the <span class="hlt">ice</span> highly desirable. While direct observations of these quantities exist, their scarcity increases with the difficulty of obtainment; the basal surfaces of terrestrial <span class="hlt">ice</span> shelves remain largely unexplored and the icy interiors of moons like Europa and Enceladus have never been directly observed. Our understanding of these entities thus relies on numerical simulation, and the efficacy of their incorporation into larger systems models is dependent on the accuracy of these initial simulations. One characteristic of seawater, likely shared by the oceans of icy moons, is that it is a solution. As such, when it is frozen a majority of the solute is rejected from the forming <span class="hlt">ice</span>, concentrating in interstitial pockets and channels, producing a two-component reactive porous media known as a mushy layer. The multiphase nature of this layer affects the evolution and dynamics of the overlying <span class="hlt">ice</span> <span class="hlt">mass</span>. Additionally <span class="hlt">ice</span> can form in the water column and accrete onto the basal surface of these <span class="hlt">ice</span> <span class="hlt">masses</span> via buoyancy driven sedimentation as frazil or platelet <span class="hlt">ice</span>. Numerical models hoping to accurately represent <span class="hlt">ice</span>-ocean interactions should include the multiphase behavior of these two phenomena. While models of sea <span class="hlt">ice</span> have begun to incorporate multiphase physics into their capabilities, no models of <span class="hlt">ice</span> shelves/shells explicitly account for the two-phase behavior of the <span class="hlt">ice</span>-ocean interface. Here we present a 1D multiphase model of floating oceanic <span class="hlt">ice</span> that includes parameterizations of both <span class="hlt">density</span> driven advection within the `mushy layer' and buoyancy driven sedimentation. The model is validated against contemporary sea <span class="hlt">ice</span> models and observational data. Environmental stresses such as supercooling and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8479X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8479X"><span><span class="hlt">Ice</span> particle <span class="hlt">mass</span>-dimensional parameter retrieval and uncertainty analysis using an Optimal Estimation framework applied to in situ data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Zhuocan; Mace, Jay; Avalone, Linnea; Wang, Zhien</p> <p>2015-04-01</p> <p>The extreme variability of <span class="hlt">ice</span> particle habits in precipitating clouds affects our understanding of these cloud systems in every aspect (i.e. radiation transfer, dynamics, precipitation rate, etc) and largely contributes to the uncertainties in the model representation of related processes. <span class="hlt">Ice</span> particle <span class="hlt">mass</span>-dimensional power law relationships, M=a*(D ^ b), are commonly assumed in models and retrieval algorithms, while very little knowledge exists regarding the uncertainties of these M-D parameters in real-world situations. In this study, we apply Optimal Estimation (OE) methodology to infer <span class="hlt">ice</span> particle <span class="hlt">mass</span>-dimensional relationship from <span class="hlt">ice</span> particle size distributions and bulk water contents independently measured on board the University of Wyoming King Air during the Colorado Airborne Multi-Phase Cloud Study (CAMPS). We also utilize W-band radar reflectivity obtained on the same platform (King Air) offering a further constraint to this ill-posed problem (Heymsfield et al. 2010). In addition to the values of retrieved M-D parameters, the associated uncertainties are conveniently acquired in the OE framework, within the limitations of assumed Gaussian statistics. We find, given the constraints provided by the bulk water measurement and in situ radar reflectivity, that the relative uncertainty of <span class="hlt">mass</span>-dimensional power law prefactor (a) is approximately 80% and the relative uncertainty of exponent (b) is 10-15%. With this level of uncertainty, the forward model uncertainty in radar reflectivity would be on the order of 4 dB or a factor of approximately 2.5 in <span class="hlt">ice</span> water content. The implications of this finding are that inferences of bulk water from either remote or in situ measurements of particle spectra cannot be more certain than this when the <span class="hlt">mass</span>-dimensional relationships are not known a priori which is almost never the case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C41A0693Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C41A0693Z"><span>Time Series of Greenland <span class="hlt">Ice</span>-Sheet Elevations and <span class="hlt">Mass</span> Changes from ICESat 2003-2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwally, H. J.; Li, J.; Medley, B.; Robbins, J. W.; Yi, D.</p> <p>2015-12-01</p> <p>We follow the repeat-track analysis (RTA) of ICESat surface-elevation data by a second stage that adjusts the measured elevations on repeat passes to the reference track taking into account the cross-track slope (αc), in order to construct elevation time series. αc are obtained from RTA simultaneous solutions for αc, dh/dt, and h0. The height measurements on repeat tracks are initially interpolated to uniform along-track reference points (every 172 m) and times (ti) giving the h(xi,ti) used in the RTA solutions. The xi are the cross-track spacings from the reference track and i is the laser campaign index. The adjusted elevation measurements at the along-track reference points are hr(ti) = h(xi,ti) - xi tan(αc) - h0. The hr(ti) time series are averaged over 50 km cells creating H(ti) series and further averaged (weighted by cell area) to H(t) time series over drainage systems (DS), elevation bands, regions, and the entire <span class="hlt">ice</span> sheet. Temperature-driven changes in the rate of firn compaction, CT(t), are calculated for 50 km cells with our firn-compaction model giving I(t) = H(t) - CT(t) - B(t) where B(t) is the vertical motion of the bedrock. During 2003 to 2009, the average dCT(t)/dt in the accumulation zone is -5 cm/yr, which amounts to a -75 km3/yr correction to <span class="hlt">ice</span> volume change estimates. The I(t) are especially useful for studying the seasonal cycle of <span class="hlt">mass</span> gains and losses and interannual variations. The H(t) for the ablation zone are fitted with a multi-variate function with a linear component describing the upward component of <span class="hlt">ice</span> flow plus winter accumulation (fall through spring) and a portion of a sine function describing the superimposed summer melting. During fall to spring the H(t) indicate that the upward motion of the <span class="hlt">ice</span> flow is at a rate of 1 m/yr, giving an annual <span class="hlt">mass</span> gain of 180 Gt/yr in the ablation zone. The summer loss from surface melting in the high-melt summer of 2005 is 350 Gt/yr, giving a net surface loss of 170 Gt/yr from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.2422L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.2422L"><span>Seasonal and Interannual Variations of Sea <span class="hlt">Ice</span> <span class="hlt">Mass</span> Balance From the Central Arctic to the Greenland Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lei, Ruibo; Cheng, Bin; Heil, Petra; Vihma, Timo; Wang, Jia; Ji, Qing; Zhang, Zhanhai</p> <p>2018-04-01</p> <p>The seasonal evolution of sea <span class="hlt">ice</span> <span class="hlt">mass</span> balance between the Central Arctic and Fram Strait, as well as the underlying driving forces, remain largely unknown because of a lack of observations. In this study, two and three buoys were deployed in the Central Arctic during the summers of 2010 and 2012, respectively. It was established that basal <span class="hlt">ice</span> growth commenced between mid-October and early December. Annual basal <span class="hlt">ice</span> growth, ranging from 0.21 to 1.14 m, was determined mainly by initial <span class="hlt">ice</span> thickness, air temperature, and oceanic heat flux during winter. An analytic thermodynamic model indicated that climate warming reduces the winter growth rate of thin <span class="hlt">ice</span> more than for thick <span class="hlt">ice</span> because of the weak thermal inertia of the former. Oceanic heat flux during the freezing season was 2-4 W m-2, which accounted for 18-31% of the basal <span class="hlt">ice</span> energy balance. We identified two mechanisms that modified the oceanic heat flux, i.e., solar energy absorbed by the upper ocean during summer, and interaction with warm waters south of Fram Strait; the latter resulted in basal <span class="hlt">ice</span> melt, even in winter. In summer 2010, <span class="hlt">ice</span> loss in the Central Arctic was considerable, which led to increased oceanic heat flux into winter and delayed <span class="hlt">ice</span> growth. The Transpolar Drift Stream was relatively weak in summer 2013. This reduced sea <span class="hlt">ice</span> advection out of the Arctic Ocean, and it restrained <span class="hlt">ice</span> melt because of the cool atmospheric conditions, weakened albedo feedback, and relatively small oceanic heat flux in the north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PolSc..10..111N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PolSc..10..111N"><span>Net <span class="hlt">mass</span> balance calculations for the Shirase Drainage Basin, east Antarctica, using the <span class="hlt">mass</span> budget method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Kazuki; Yamanokuchi, Tsutomu; Doi, Koichiro; Shibuya, Kazuo</p> <p>2016-06-01</p> <p>We quantify the <span class="hlt">mass</span> budget of the Shirase drainage basin (SHI), Antarctica, by separately estimating snow accumulation (surface <span class="hlt">mass</span> balance; SMB) and glacier <span class="hlt">ice</span> <span class="hlt">mass</span> discharge (IMD). We estimated the SMB in the SHI, using a regional atmospheric climate model (RACMO2.1). The SMB of the mainstream A flow region was 12.1 ± 1.5 Gt a-1 for an area of 1.985 × 105 km2. Obvious overestimation of the model round the coast, ∼0.5 Gt a-1, was corrected for. For calculating the IMD, we employed a 15-m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with a digital elevation model (DEM) to determine the heights at the grounding line (GL), after comparison with the interpolated Bamber DEM grid heights; the results of this are referred to as the measured heights. <span class="hlt">Ice</span> thickness data at the GL were inferred by using a free-board relationship between the measured height and the <span class="hlt">ice</span> thickness, and considering the measured firn depth correction (4.2 m with the reference <span class="hlt">ice</span> <span class="hlt">density</span> of 910 kg m-3) for the nearby blue-<span class="hlt">ice</span> area. The total IMD was estimated to be 14.0 ± 1.8 Gt a-1. Semi-empirical firn densification model gives the estimate within 0.1-0.2 Gt a-1 difference. The estimated net <span class="hlt">mass</span> balance, -1.9 Gt a-1, has a two-σ uncertainty of ±3.3 Gt a-1, and probable melt water discharge strongly suggests negative NMB, although the associated uncertainty is large.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMED34A..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMED34A..05S"><span>Incorporating Geodetic Data in Introductory Geoscience Classrooms through UNAVCO's GETSI "<span class="hlt">Ice</span> <span class="hlt">Mass</span> and Sea Level Changes" Module</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stearns, L. A.; Walker, B.; Pratt-Sitaula, B.</p> <p>2015-12-01</p> <p>GETSI (Geodesy Tools for Societal Issues) is an NSF-funded partnership program between UNAVCO, Indiana University, Mt. San Antonio College, and the Science Education Resource Center (SERC). We present results from classroom testing and assessment of the GETSI <span class="hlt">Ice</span> <span class="hlt">Mass</span> and Sea Level Changes module that utilizes geodetic data to teach about <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss in introductory undergraduate courses. The module explores the interactions between global sea level rise, Greenland <span class="hlt">ice</span> <span class="hlt">mass</span> loss, and the response of the solid Earth. It brings together topics typically addressed in introductory Earth science courses (isostatic rebound, geologic measurements, and climate change) in a way that highlights the interconnectivity of the Earth system and the interpretation of geodetic data. The module was tested 3 times at 3 different institution types (R1 institution, comprehensive university, and community college), and formative and summative assessment data were obtained. We will provide an overview of the instructional materials, describe our teaching methods, and discuss how formative and summative assessment data assisted in revisions of the teaching materials and changes in our pedagogy during subsequent implementation of the module. We will also provide strategies for faculty who wish to incorporate the module into their curricula. Instructional materials, faculty and student resources, and implementation tips are freely available on the GETSI website.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5813910','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5813910"><span>A <span class="hlt">mass-density</span> model can account for the size-weight illusion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bergmann Tiest, Wouter M.; Drewing, Knut</p> <p>2018-01-01</p> <p>When judging the heaviness of two objects with equal <span class="hlt">mass</span>, people perceive the smaller and denser of the two as being heavier. Despite the large number of theories, covering bottom-up and top-down approaches, none of them can fully account for all aspects of this size-weight illusion and thus for human heaviness perception. Here we propose a new maximum-likelihood estimation model which describes the illusion as the weighted average of two heaviness estimates with correlated noise: One estimate derived from the object’s <span class="hlt">mass</span>, and the other from the object’s <span class="hlt">density</span>, with estimates’ weights based on their relative reliabilities. While information about <span class="hlt">mass</span> can directly be perceived, information about <span class="hlt">density</span> will in some cases first have to be derived from <span class="hlt">mass</span> and volume. However, according to our model at the crucial perceptual level, heaviness judgments will be biased by the objects’ <span class="hlt">density</span>, not by its size. In two magnitude estimation experiments, we tested model predictions for the visual and the haptic size-weight illusion. Participants lifted objects which varied in <span class="hlt">mass</span> and <span class="hlt">density</span>. We additionally varied the reliability of the <span class="hlt">density</span> estimate by varying the quality of either visual (Experiment 1) or haptic (Experiment 2) volume information. As predicted, with increasing quality of volume information, heaviness judgments were increasingly biased towards the object’s <span class="hlt">density</span>: Objects of the same <span class="hlt">density</span> were perceived as more similar and big objects were perceived as increasingly lighter than small (denser) objects of the same <span class="hlt">mass</span>. This perceived difference increased with an increasing difference in <span class="hlt">density</span>. In an additional two-alternative forced choice heaviness experiment, we replicated that the illusion strength increased with the quality of volume information (Experiment 3). Overall, the results highly corroborate our model, which seems promising as a starting point for a unifying framework for the size-weight illusion and human heaviness</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29447183','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29447183"><span>A <span class="hlt">mass-density</span> model can account for the size-weight illusion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wolf, Christian; Bergmann Tiest, Wouter M; Drewing, Knut</p> <p>2018-01-01</p> <p>When judging the heaviness of two objects with equal <span class="hlt">mass</span>, people perceive the smaller and denser of the two as being heavier. Despite the large number of theories, covering bottom-up and top-down approaches, none of them can fully account for all aspects of this size-weight illusion and thus for human heaviness perception. Here we propose a new maximum-likelihood estimation model which describes the illusion as the weighted average of two heaviness estimates with correlated noise: One estimate derived from the object's <span class="hlt">mass</span>, and the other from the object's <span class="hlt">density</span>, with estimates' weights based on their relative reliabilities. While information about <span class="hlt">mass</span> can directly be perceived, information about <span class="hlt">density</span> will in some cases first have to be derived from <span class="hlt">mass</span> and volume. However, according to our model at the crucial perceptual level, heaviness judgments will be biased by the objects' <span class="hlt">density</span>, not by its size. In two magnitude estimation experiments, we tested model predictions for the visual and the haptic size-weight illusion. Participants lifted objects which varied in <span class="hlt">mass</span> and <span class="hlt">density</span>. We additionally varied the reliability of the <span class="hlt">density</span> estimate by varying the quality of either visual (Experiment 1) or haptic (Experiment 2) volume information. As predicted, with increasing quality of volume information, heaviness judgments were increasingly biased towards the object's <span class="hlt">density</span>: Objects of the same <span class="hlt">density</span> were perceived as more similar and big objects were perceived as increasingly lighter than small (denser) objects of the same <span class="hlt">mass</span>. This perceived difference increased with an increasing difference in <span class="hlt">density</span>. In an additional two-alternative forced choice heaviness experiment, we replicated that the illusion strength increased with the quality of volume information (Experiment 3). Overall, the results highly corroborate our model, which seems promising as a starting point for a unifying framework for the size-weight illusion and human heaviness perception.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70015528','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70015528"><span><span class="hlt">Mass</span> balance and sliding velocity of the Puget lobe of the cordilleran <span class="hlt">ice</span> sheet during the last glaciation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Booth, D.B.</p> <p>1986-01-01</p> <p>An estimate of the sliding velocity and basal meltwater discharge of the Puget lobe of the Cordilleran <span class="hlt">ice</span> sheet can be calculated from its reconstructed extent, altitude, and <span class="hlt">mass</span> balance. Lobe dimensions and surface altitudes are inferred from <span class="hlt">ice</span> limits and flow-direction indicators. Net annual <span class="hlt">mass</span> balance and total ablation are calculated from relations empirically derived from modern maritime glaciers. An equilibrium-line altitude between 1200 and 1250 m is calculated for the maximum glacial advance (ca. 15,000 yr B.P.) during the Vashon Stade of the Fraser Glaciation. This estimate is in accord with geologic data and is insensitive to plausible variability in the parameters used in the reconstruction. Resultant sliding velocities are as much as 650 m/a at the equilibrium line, decreasing both up- and downglacier. Such velocities for an <span class="hlt">ice</span> sheet of this size are consistent with nonsurging behavior. Average meltwater discharge increases monotonically downglacier to 3000 m3/sec at the terminus and is of a comparable magnitude to <span class="hlt">ice</span> discharge over much of the glacier's ablation area. Palcoclimatic inferences derived from this reconstruction are consistent with previous, independently derived studies of late Pleistocene temperature and precipitation in the Pacific Northwest. ?? 1986.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006686','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006686"><span>Altitude Effects on Thermal <span class="hlt">Ice</span> Protection System Performance; a Study of an Alternative Approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Addy, Harold E., Jr.; Orchard, David; Wright, William B.; Oleskiw, Myron</p> <p>2016-01-01</p> <p>Research has been conducted to better understand the phenomena involved during operation of an aircraft's thermal <span class="hlt">ice</span> protection system under running wet <span class="hlt">icing</span> conditions. In such situations, supercooled water striking a thermally <span class="hlt">ice</span>-protected surface does not fully evaporate but runs aft to a location where it freezes. The effects of altitude, in terms of air pressure and <span class="hlt">density</span>, on the processes involved were of particular interest. Initial study results showed that the altitude effects on heat energy transfer were accurately modeled using existing methods, but water <span class="hlt">mass</span> transport was not. Based upon those results, a new method to account for altitude effects on thermal <span class="hlt">ice</span> protection system operation was proposed. The method employs a two-step process where heat energy and <span class="hlt">mass</span> transport are sequentially matched, linked by matched surface temperatures. While not providing exact matching of heat and <span class="hlt">mass</span> transport to reference conditions, the method produces a better simulation than other methods. Moreover, it does not rely on the application of empirical correction factors, but instead relies on the straightforward application of the primary physics involved. This report describes the method, shows results of testing the method, and discusses its limitations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513583C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513583C"><span><span class="hlt">Ice</span> shelf breaking and increase velocity of glacier: the view from analogue experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Corti, Giacomo; Iandelli, Irene</p> <p>2013-04-01</p> <p>Collapse of the Larsen II platform during the late 90s has generated an increase in velocity if <span class="hlt">ice</span> sheet discharge, highlighting that these processes may strongly destabilize large <span class="hlt">ice</span> <span class="hlt">masses</span> speeding up the plateau discharge toward the sea. Parameters such as <span class="hlt">ice</span> thickness, valley width and slope, <span class="hlt">ice</span> pack dimensions may contribute to modulate the effect of increase in <span class="hlt">ice</span> flow velocity following the removal of <span class="hlt">ice</span>. We analyze this process through scale analogue models, aimed at reproducing the flow of <span class="hlt">ice</span> from a plateau into the sea through a narrow valley. The <span class="hlt">ice</span> is reproduced with a transparent silicone (Polydimethisiloxane), flowing at velocities of a few centimeters per hour and simulating natural velocities in the range of a few meters per year. Having almost the same <span class="hlt">density</span> of the <span class="hlt">ice</span>, PDMS floats on water and simulate the <span class="hlt">ice</span>-shelf formation. Results of preliminary experimental series support that this methodology is able to reasonably reproduce the process and support a significant increase in velocity discharge following the removal of <span class="hlt">ice</span> pack. Additional tests are designed to verify the influence of the above-mentioned parameters on the increase in <span class="hlt">ice</span> velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C13D..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C13D..07M"><span>A laboratory scale model of abrupt <span class="hlt">ice</span>-shelf disintegration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Macayeal, D. R.; Boghosian, A.; Styron, D. D.; Burton, J. C.; Amundson, J. M.; Cathles, L. M.; Abbot, D. S.</p> <p>2010-12-01</p> <p>An important mode of Earth’s disappearing cryosphere is the abrupt disintegration of <span class="hlt">ice</span> shelves along the Peninsula of Antarctica. This disintegration process may be triggered by climate change, however the work needed to produce the spectacular, explosive results witnessed with the Larsen B and Wilkins <span class="hlt">ice</span>-shelf events of the last decade comes from the large potential energy release associated with iceberg capsize and fragmentation. To gain further insight into the underlying exchanges of energy involved in <span class="hlt">massed</span> iceberg movements, we have constructed a laboratory-scale model designed to explore the physical and hydrodynamic interactions between icebergs in a confined channel of water. The experimental apparatus consists of a 2-meter water tank that is 30 cm wide. Within the tank, we introduce fresh water and approximately 20-100 rectangular plastic ‘icebergs’ having the appropriate <span class="hlt">density</span> contrast with water to mimic <span class="hlt">ice</span>. The blocks are initially deployed in a tight pack, with all blocks arranged in a manner to represent the initial state of an integrated <span class="hlt">ice</span> shelf or <span class="hlt">ice</span> tongue. The system is allowed to evolve through time under the driving forces associated with iceberg hydrodynamics. Digitized videography is used to quantify how the system of plastic icebergs evolves between states of quiescence to states of mobilization. Initial experiments show that, after a single ‘agitator’ iceberg begins to capsize, an ‘avalanche’ of capsizing icebergs ensues which drives horizontal expansion of the <span class="hlt">massed</span> icebergs across the water surface, and which stimulates other icebergs to capsize. A surprise initially evident in the experiments is the fact that the kinetic energy of the expanding <span class="hlt">mass</span> of icebergs is only a small fraction of the net potential energy released by the rearrangement of <span class="hlt">mass</span> via capsize. Approximately 85 - 90 % of the energy released by the system goes into water motion modes, including a pervasive, easily observed seich mode of the tank</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRF..122.2324S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRF..122.2324S"><span>Assimilating the <span class="hlt">ICE</span>-6G_C Reconstruction of the Latest Quaternary <span class="hlt">Ice</span> Age Cycle Into Numerical Simulations of the Laurentide and Fennoscandian <span class="hlt">Ice</span> Sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stuhne, G. R.; Peltier, W. R.</p> <p>2017-12-01</p> <p>We analyze the effects of nudging 100 kyr numerical simulations of the Laurentide and Fennoscandian <span class="hlt">ice</span> sheets toward the glacial isostatic adjustment-based (GIA-based) <span class="hlt">ICE</span>-6G_C reconstruction of the most recent <span class="hlt">ice</span> age cycle. Starting with the <span class="hlt">ice</span> physics approximations of the PISM <span class="hlt">ice</span> sheet model and the SeaRISE simulation protocols, we incorporate nudging at characteristic time scales, τf, through anomalous <span class="hlt">mass</span> balance terms in the <span class="hlt">ice</span> <span class="hlt">mass</span> conservation equation. As should be expected, these <span class="hlt">mass</span> balances exhibit physically unrealistic details arising from pure GIA-based reconstruction geometry when nudging is very strong (τf=20 years for North America), while weakly nudged (τf=1,000 years) solutions deviate from <span class="hlt">ICE</span>-6G_C sufficiently to degrade its observational fit quality. For reasonable intermediate time scales (τf=100 years and 200 years), we perturbatively analyze nudged <span class="hlt">ice</span> dynamics as a superposition of "leading-order smoothing" that diffuses <span class="hlt">ICE</span>-6G_C in a physically and observationally consistent manner and "higher-order" deviations arising, for instance, from biases in the time dependence of surface climate boundary conditions. Based upon the relative deviations between respective nudged simulations in which these biases follow surface temperature from <span class="hlt">ice</span> cores and eustatic sea level from marine sediment cores, we compute "<span class="hlt">ice</span> core climate adjustments" that suggest how local paleoclimate observations may be applied to the systematic refinement of <span class="hlt">ICE</span>-6G_C. Our results are consistent with a growing body of evidence suggesting that the geographical origins of Meltwater Pulse 1B (MWP1b) may lie primarily in North America as opposed to Antarctica (as reconstructed in <span class="hlt">ICE</span>-6G_C).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890018779','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890018779"><span><span class="hlt">Ice</span> sheet radar altimetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, J.</p> <p>1988-01-01</p> <p>The surface topography of the Greenland and Antarctic <span class="hlt">ice</span> sheets between 72 degrees north and south was mapped using radar altimetry data from the U.S. Navy GEOSAT. The glaciological objectives of this activity were to study the dynamics of the <span class="hlt">ice</span> flow, changes in the position of floating <span class="hlt">ice</span>-shelf fronts, and ultimately to measure temporal changes in <span class="hlt">ice</span> surface elevation indicative of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P53E2187S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P53E2187S"><span>Geomorphological Evidence for Pervasive Ground <span class="hlt">Ice</span> on Ceres from Dawn Observations of Craters and Flows.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, B. E.; Chilton, H.; Hughson, K.; Scully, J. E. C.; Russell, C. T.; Sizemore, H. G.; Nathues, A.; Platz, T.; Bland, M. T.; Schenk, P.; Hiesinger, H.; Jaumann, R.; Byrne, S.; Schorghofer, N.; Ammannito, E.; Marchi, S.; O'Brien, D. P.; Sykes, M. V.; Le Corre, L.; Capria, M. T.; Reddy, V.; Raymond, C. A.; Mest, S. C.; Feldman, W. C.</p> <p>2015-12-01</p> <p>Five decades of observations of Ceres' albedo, surface composition, shape and <span class="hlt">density</span> suggest that Ceres is comprised of both silicates and tens of percent of <span class="hlt">ice</span>. Historical suggestions of surficial hydrated silicates and evidence for water emission, coupled with its bulk <span class="hlt">density</span> of ~2100 kg/m3 and Dawn observations of young craters containing high albedo spots support this conclusion. We report geomorphological evidence from survey data demonstrating that evaporative and fluid-flow processes within silicate-<span class="hlt">ice</span> mixtures are prevalent on Ceres, and indicate that its surface materials contain significant water <span class="hlt">ice</span>. Here we highlight three classes of features that possess strong evidence for ground <span class="hlt">ice</span>. First, ubiquitous scalloped and "breached" craters are characterized by <span class="hlt">mass</span> wasting and by the recession of crater walls in asymmetric patterns; these appear analogous to scalloped terrain on Mars and protalus lobes formed by <span class="hlt">mass</span> wasting in terrestrial glaciated regions. The degradation of crater walls appears to be responsible for the nearly complete removal of some craters, particularly at low latitudes. Second, several high latitude, high elevation craters feature lobed flows that emanate from cirque-shaped head walls and bear strikingly similar morphology to terrestrial rock glaciers. These similarities include lobate toes and indications of furrows and ridges consistent with <span class="hlt">ice</span>-cored or <span class="hlt">ice</span>-cemented material. Other lobed flows persist at the base of crater walls and <span class="hlt">mass</span> wasting features. Many flow features evidently terminate at ramparts. Third, there are frequent irregular domes, peaks and mounds within crater floors that depart from traditional crater central peaks or peak complexes. In some cases the irregular domes show evidence for high albedo or activity, and thus given other evidence for <span class="hlt">ice</span>, these could be due to local melt and extrusion via hydrologic gradients, forming domes similar to pingos. The global distribution of these classes of features</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050237849','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050237849"><span>Characterization of <span class="hlt">Ice</span> for Return-to-Flight of the Space Shuttle. Part 2; Soft <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schulson, Erland M.; Iliescu, Daniel</p> <p>2005-01-01</p> <p>In support of characterizing <span class="hlt">ice</span> debris for return-to-flight (RTF) of NASA's space shuttle, we have determined the microstructure, <span class="hlt">density</span> and compressive strength (at -10 C at approximately 0.3 per second) of porous or soft <span class="hlt">ice</span> that was produced from both atmospheric water and consolidated snow. The study showed that the atmospheric material was generally composed of a mixture of very fine (0.1 to 0.3 millimeters) and coarser (5 to 10 millimeter) grains, plus air bubbles distributed preferentially within the more finely-grained part of the microstructure. The snow <span class="hlt">ice</span> was composed of even finer grains (approximately 0.05 millimeters) and contained more pores. Correspondingly, the snow <span class="hlt">ice</span> was of lower <span class="hlt">density</span> than the atmospheric <span class="hlt">ice</span> and both materials were significantly less dense than hard <span class="hlt">ice</span>. The atmospheric <span class="hlt">ice</span> was stronger (approximately 3.8 MPa) than the snow <span class="hlt">ice</span> (approximately 1.9 MPa), but weaker by a factor of 2 to 5 than pore-free hard <span class="hlt">ice</span> deformed under the same conditions. Zero Values are given for Young's modulus, compressive strength and Poisson's ratio that can be used for modeling soft <span class="hlt">ice</span> from the external tank (ET).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3174F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3174F"><span>Validation and Interpretation of a new sea <span class="hlt">ice</span> Glob<span class="hlt">Ice</span> dataset using buoys and the CICE sea <span class="hlt">ice</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flocco, D.; Laxon, S. W.; Feltham, D. L.; Haas, C.</p> <p>2012-04-01</p> <p>The Glob<span class="hlt">Ice</span> project has provided high resolution sea <span class="hlt">ice</span> product datasets over the Arctic derived from SAR data in the ESA archive. The products are validated sea <span class="hlt">ice</span> motion, deformation and fluxes through straits. Glob<span class="hlt">Ice</span> sea <span class="hlt">ice</span> velocities, deformation data and sea <span class="hlt">ice</span> concentration have been validated using buoy data provided by the International Arctic Buoy Program (IABP). Over 95% of the Glob<span class="hlt">Ice</span> and buoy data analysed fell within 5 km of each other. The Glob<span class="hlt">Ice</span> Eulerian image pair product showed a high correlation with buoy data. The sea <span class="hlt">ice</span> concentration product was compared to SSM/I data. An evaluation of the validity of the Glob<span class="hlt">ICE</span> data will be presented in this work. Glob<span class="hlt">ICE</span> sea <span class="hlt">ice</span> velocity and deformation were compared with runs of the CICE sea <span class="hlt">ice</span> model: in particular the <span class="hlt">mass</span> fluxes through the straits were used to investigate the correlation between the winter behaviour of sea <span class="hlt">ice</span> and the sea <span class="hlt">ice</span> state in the following summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17731883','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17731883"><span><span class="hlt">Ice</span> core evidence for extensive melting of the greenland <span class="hlt">ice</span> sheet in the last interglacial.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koerner, R M</p> <p>1989-05-26</p> <p>Evidence from <span class="hlt">ice</span> at the bottom of <span class="hlt">ice</span> cores from the Canadian Arctic Islands and Camp Century and Dye-3 in Greenland suggests that the Greenland <span class="hlt">ice</span> sheet melted extensively or completely during the last interglacial period more than 100 ka (thousand years ago), in contrast to earlier interpretations. The presence of dirt particles in the basal <span class="hlt">ice</span> has previously been thought to indicate that the base of the <span class="hlt">ice</span> sheets had melted and that the evidence for the time of original growth of these <span class="hlt">ice</span> <span class="hlt">masses</span> had been destroyed. However, the particles most likely blew onto the <span class="hlt">ice</span> when the dimensions of the <span class="hlt">ice</span> caps and <span class="hlt">ice</span> sheets were much smaller. <span class="hlt">Ice</span> texture, gas content, and other evidence also suggest that the basal <span class="hlt">ice</span> at each drill site is superimposed <span class="hlt">ice</span>, a type of <span class="hlt">ice</span> typical of the early growth stages of an <span class="hlt">ice</span> cap or <span class="hlt">ice</span> sheet. If the present-day <span class="hlt">ice</span> <span class="hlt">masses</span> began their growth during the last interglacial, the <span class="hlt">ice</span> sheet from the earlier (Illinoian) glacial period must have competely or largely melted during the early part of the same interglacial period. If such melting did occur, the 6-meter higher-than-present sea level during the Sangamon cannot be attributed to disintegration of the West Antarctic <span class="hlt">ice</span> sheet, as has been suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.G31C0931W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.G31C0931W"><span>Temporal and spatial variabilities of Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> changes inferred by GRACE in a Bayesian framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, L.; Davis, J. L.; Tamisiea, M. E.</p> <p>2017-12-01</p> <p>The Antarctic <span class="hlt">ice</span> sheet (AIS) holds about 60% of all fresh water on the Earth, an amount equivalent to about 58 m of sea-level rise. Observation of AIS <span class="hlt">mass</span> change is thus essential in determining and predicting its contribution to sea level. While the <span class="hlt">ice</span> <span class="hlt">mass</span> loss estimates for West Antarctica (WA) and the Antarctic Peninsula (AP) are in good agreement, what the <span class="hlt">mass</span> balance over East Antarctica (EA) is, and whether or not it compensates for the <span class="hlt">mass</span> loss is under debate. Besides the different error sources and sensitivities of different measurement types, complex spatial and temporal variabilities would be another factor complicating the accurate estimation of the AIS <span class="hlt">mass</span> balance. Therefore, a model that allows for variabilities in both melting rate and seasonal signals would seem appropriate in the estimation of present-day AIS melting. We present a stochastic filter technique, which enables the Bayesian separation of the systematic stripe noise and <span class="hlt">mass</span> signal in decade-length GRACE monthly gravity series, and allows the estimation of time-variable seasonal and inter-annual components in the signals. One of the primary advantages of this Bayesian method is that it yields statistically rigorous uncertainty estimates reflecting the inherent spatial resolution of the data. By applying the stochastic filter to the decade-long GRACE observations, we present the temporal variabilities of the AIS <span class="hlt">mass</span> balance at basin scale, particularly over East Antarctica, and decipher the EA <span class="hlt">mass</span> variations in the past decade, and their role in affecting overall AIS <span class="hlt">mass</span> balance and sea level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910364J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910364J"><span>A Simple Diagnostic Model of the Circulation Beneath an <span class="hlt">Ice</span> Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jenkins, Adrian; Nøst, Ole Anders</p> <p>2017-04-01</p> <p>The ocean circulation beneath <span class="hlt">ice</span> shelves supplies the heat required to melt <span class="hlt">ice</span> and exports the resulting freshwater. It therefore plays a key role in determining the <span class="hlt">mass</span> balance and geometry of the <span class="hlt">ice</span> shelves and hence the restraint they impose on the outflow of grounded <span class="hlt">ice</span> from the interior of the <span class="hlt">ice</span> sheet. Despite this critical role in regulating the <span class="hlt">ice</span> sheet's contribution to eustatic sea level, an understanding of some of the most basic features of the circulation is lacking. The conventional paradigm is one of a buoyancy-forced overturning circulation, with inflow of warm, salty water along the seabed and outflow of cooled and freshened waters along the <span class="hlt">ice</span> base. However, most sub-<span class="hlt">ice</span>-shelf cavities are broad relative to the internal Rossby radius, so a horizontal circulation accompanies the overturning. Primitive equation ocean models applied to idealised geometries produce cyclonic gyres of comparable magnitude, but in the absence of a theoretical understanding of what controls the gyre strength, those solutions can only be validated against each other. Furthermore, we have no understanding of how the gyre circulation should change given more complex geometries. To begin to address this gap in our theoretical understanding we present a simple, linear, steady-state model for the circulation beneath an <span class="hlt">ice</span> shelf. Our approach in analogous to that of Stommel's classic analysis of the wind-driven gyres, but is complicated by the fact that his most basic assumption of homogeneity is inappropriate. The only forcing on the flow beneath an <span class="hlt">ice</span> shelf arises because of the horizontal <span class="hlt">density</span> gradients set up by melting. We thus arrive at a diagnostic model which gives us the depth-dependent horizontal circulation that results from an imposed geometry and <span class="hlt">density</span> distribution. We describe the development of the model and present some preliminary solutions for the simplest cavity geometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C23C0798L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C23C0798L"><span>How much can Greenland melt? An upper bound on <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet through surface melting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, X.; Bassis, J. N.</p> <p>2015-12-01</p> <p>With observations showing accelerated <span class="hlt">mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet due to surface melt, the Greenland <span class="hlt">Ice</span> Sheet is becoming one of the most significant contributors to sea level rise. The contribution of the Greenland <span class="hlt">Ice</span> Sheet o sea level rise is likely to accelerate in the coming decade and centuries as atmospheric temperatures continue to rise, potentially triggering ever larger surface melt rates. However, at present considerable uncertainty remains in projecting the contribution to sea level of the Greenland <span class="hlt">Ice</span> Sheet both due to uncertainty in atmospheric forcing and the <span class="hlt">ice</span> sheet response to climate forcing. Here we seek an upper bound on the contribution of surface melt from the Greenland to sea level rise in the coming century using a surface energy balance model coupled to an englacial model. We use IPCC Representative Concentration Pathways (RCP8.5, RCP6, RCP4.5, RCP2.6) climate scenarios from an ensemble of global climate models in our simulations to project the maximum rate of <span class="hlt">ice</span> volume loss and related sea-level rise associated with surface melting. To estimate the upper bound, we assume the Greenland <span class="hlt">Ice</span> Sheet is perpetually covered in thick clouds, which maximize longwave radiation to the <span class="hlt">ice</span> sheet. We further assume that deposition of black carbon darkens the <span class="hlt">ice</span> substantially turning it nearly black, substantially reducing its albedo. Although assuming that all melt water not stored in the snow/firn is instantaneously transported off the <span class="hlt">ice</span> sheet increases <span class="hlt">mass</span> loss in the short term, refreezing of retained water warms the <span class="hlt">ice</span> and may lead to more melt in the long term. Hence we examine both assumptions and use the scenario that leads to the most surface melt by 2100. Preliminary models results suggest that under the most aggressive climate forcing, surface melt from the Greenland <span class="hlt">Ice</span> Sheet contributes ~1 m to sea level by the year 2100. This is a significant contribution and ignores dynamic effects. We also examined a lower bound</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25550506','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25550506"><span>Parasitism alters three power laws of scaling in a metazoan community: Taylor's law, <span class="hlt">density-mass</span> allometry, and variance-<span class="hlt">mass</span> allometry.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lagrue, Clément; Poulin, Robert; Cohen, Joel E</p> <p>2015-02-10</p> <p>How do the lifestyles (free-living unparasitized, free-living parasitized, and parasitic) of animal species affect major ecological power-law relationships? We investigated this question in metazoan communities in lakes of Otago, New Zealand. In 13,752 samples comprising 1,037,058 organisms, we found that species of different lifestyles differed in taxonomic distribution and body <span class="hlt">mass</span> and were well described by three power laws: a spatial Taylor's law (the spatial variance in population <span class="hlt">density</span> was a power-law function of the spatial mean population <span class="hlt">density</span>); <span class="hlt">density-mass</span> allometry (the spatial mean population <span class="hlt">density</span> was a power-law function of mean body <span class="hlt">mass</span>); and variance-<span class="hlt">mass</span> allometry (the spatial variance in population <span class="hlt">density</span> was a power-law function of mean body <span class="hlt">mass</span>). To our knowledge, this constitutes the first empirical confirmation of variance-<span class="hlt">mass</span> allometry for any animal community. We found that the parameter values of all three relationships differed for species with different lifestyles in the same communities. Taylor's law and <span class="hlt">density-mass</span> allometry accurately predicted the form and parameter values of variance-<span class="hlt">mass</span> allometry. We conclude that species of different lifestyles in these metazoan communities obeyed the same major ecological power-law relationships but did so with parameters specific to each lifestyle, probably reflecting differences among lifestyles in population dynamics and spatial distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1175859','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1175859"><span>Methods and apparatus for rotor blade <span class="hlt">ice</span> detection</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>LeMieux, David Lawrence</p> <p>2006-08-08</p> <p>A method for detecting <span class="hlt">ice</span> on a wind turbine having a rotor and one or more rotor blades each having blade roots includes monitoring meteorological conditions relating to <span class="hlt">icing</span> conditions and monitoring one or more physical characteristics of the wind turbine in operation that vary in accordance with at least one of the <span class="hlt">mass</span> of the one or more rotor blades or a <span class="hlt">mass</span> imbalance between the rotor blades. The method also includes using the one or more monitored physical characteristics to determine whether a blade <span class="hlt">mass</span> anomaly exists, determining whether the monitored meteorological conditions are consistent with blade <span class="hlt">icing</span>; and signaling an <span class="hlt">icing</span>-related blade <span class="hlt">mass</span> anomaly when a blade <span class="hlt">mass</span> anomaly is determined to exist and the monitored meteorological conditions are determined to be consistent with <span class="hlt">icing</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/23624','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/23624"><span>Forecasting gypsy moth egg-<span class="hlt">mass</span> <span class="hlt">density</span></span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Robert W. Campbell; Robert W. Campbell</p> <p>1973-01-01</p> <p>Several multiple regression models for gypsy moth egg-<span class="hlt">mass</span> <span class="hlt">density</span> were developed from data accumulated in eastern New England between 1911 and 1931. Analysis of these models indicates that: (1) The gypsy moth population system was relatively stable in either the OUTBREAK phase or the INNOCUOUS one; (2) Several naturally occurring processes that could terminate the...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080023352&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080023352&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber"><span>Rapid <span class="hlt">Ice</span> <span class="hlt">Mass</span> Loss: Does It Have an Influence on Earthquake Occurrence in Southern Alaska?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sauber, Jeanne M.</p> <p>2008-01-01</p> <p>The glaciers of southern Alaska are extensive, and many of them have undergone gigatons of <span class="hlt">ice</span> wastage on time scales on the order of the seismic cycle. Since the <span class="hlt">ice</span> loss occurs directly above a shallow main thrust zone associated with subduction of the Pacific-Yakutat plate beneath continental Alaska, the region between the Malaspina and Bering Glaciers is an excellent test site for evaluating the importance of recent <span class="hlt">ice</span> wastage on earthquake faulting potential. We demonstrate the influence of cumulative glacial <span class="hlt">mass</span> loss following the 1899 Yakataga earthquake (M=8.1) by using a two dimensional finite element model with a simple representation of <span class="hlt">ice</span> fluctuations to calculate the incremental stresses and change in the fault stability margin (FSM) along the main thrust zone (MTZ) and on the surface. Along the MTZ, our results indicate a decrease in FSM between 1899 and the 1979 St. Elias earthquake (M=7.4) of 0.2 - 1.2 MPa over an 80 km region between the coast and the 1979 aftershock zone; at the surface, the estimated FSM was larger but more localized to the lower reaches of glacial ablation zones. The <span class="hlt">ice</span>-induced stresses were large enough, in theory, to promote the occurrence of shallow thrust earthquakes. To empirically test the influence of short-term <span class="hlt">ice</span> fluctuations on fault stability, we compared the seismic rate from a reference background time period (1988-1992) against other time periods (1993-2006) with variable <span class="hlt">ice</span> or tectonic change characteristics. We found that the frequency of small tectonic events in the Icy Bay region increased in 2002-2006 relative to the background seismic rate. We hypothesize that this was due to a significant increase in the rate of <span class="hlt">ice</span> wastage in 2002-2006 instead of the M=7.9, 2002 Denali earthquake, located more than 100km away.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27386524','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27386524"><span>Monitoring southwest Greenland's <span class="hlt">ice</span> sheet melt with ambient seismic noise.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mordret, Aurélien; Mikesell, T Dylan; Harig, Christopher; Lipovsky, Bradley P; Prieto, Germán A</p> <p>2016-05-01</p> <p>The Greenland <span class="hlt">ice</span> sheet presently accounts for ~70% of global <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss. Because this <span class="hlt">mass</span> loss is associated with sea-level rise at a rate of 0.7 mm/year, the development of improved monitoring techniques to observe ongoing changes in <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance is of paramount concern. Spaceborne <span class="hlt">mass</span> balance techniques are commonly used; however, they are inadequate for many purposes because of their low spatial and/or temporal resolution. We demonstrate that small variations in seismic wave speed in Earth's crust, as measured with the correlation of seismic noise, may be used to infer seasonal <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance. Seasonal loading and unloading of glacial <span class="hlt">mass</span> induces strain in the crust, and these strains then result in seismic velocity changes due to poroelastic processes. Our method provides a new and independent way of monitoring (in near real time) <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance, yielding new constraints on <span class="hlt">ice</span> sheet evolution and its contribution to global sea-level changes. An increased number of seismic stations in the vicinity of <span class="hlt">ice</span> sheets will enhance our ability to create detailed space-time records of <span class="hlt">ice</span> <span class="hlt">mass</span> variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.G11A0909M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.G11A0909M"><span>Using aerogravity and seismic data to model the bathymetry and upper crustal structure beneath the Pine Island Glacier <span class="hlt">ice</span> shelf, West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muto, A.; Peters, L. E.; Anandakrishnan, S.; Alley, R. B.; Riverman, K. L.</p> <p>2013-12-01</p> <p>Recent estimates indicate that <span class="hlt">ice</span> shelves along the Amundsen Sea coast in West Antarctica are losing substantial <span class="hlt">mass</span> through sub-<span class="hlt">ice</span>-shelf melting and contributing to the accelerating <span class="hlt">mass</span> loss of the grounded <span class="hlt">ice</span> buttressed by them. For Pine Island Glacier (PIG), relatively warm Circumpolar Deep Water has been identified as the key driver of the sub-<span class="hlt">ice</span>-shelf melting although poor constraints on PIG sub-<span class="hlt">ice</span> shelf have restricted thorough understanding of these <span class="hlt">ice</span>-ocean interactions. Aerogravity data from NASA's Operation <span class="hlt">Ice</span>Bridge (OIB) have been useful in identifying large-scale (on the order of ten kilometers) features but the results have relatively large uncertainties due to the inherent non-uniqueness of the gravity inversion. Seismic methods offer the most direct means of providing water thickness and upper crustal geological constraints, but availability of such data sets over the PIG <span class="hlt">ice</span> shelf has been limited due to logistical constraints. Here we present a comparative analysis of the bathymetry and upper crustal structure beneath the <span class="hlt">ice</span> shelf of PIG through joint inversion of OIB aerogravity data and in situ active-source seismic measurements collected in the 2012-13 austral summer. Preliminary results indicate improved resolution of the ocean cavity, particularly in the interior and sides of the PIG <span class="hlt">ice</span> shelf, and sedimentary drape across the region. Seismically derived variations in <span class="hlt">ice</span> and ocean water <span class="hlt">densities</span> are also applied to the gravity inversion to produce a more robust model of PIG sub-<span class="hlt">ice</span> shelf structure, as opposed to commonly used single <span class="hlt">ice</span> and water <span class="hlt">densities</span> across the entire study region. Misfits between the seismically-constrained gravity inversion and that estimated previously from aerogravity alone provide insights on the sensitivity of gravity measurements to model perturbations and highlight the limitations of employing gravity data to model <span class="hlt">ice</span> shelf environments when no other sub-<span class="hlt">ice</span> constraints are available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12368852','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12368852"><span>Switch of flow direction in an Antarctic <span class="hlt">ice</span> stream.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Conway, H; Catania, G; Raymond, C F; Gades, A M; Scambos, T A; Engelhardt, H</p> <p>2002-10-03</p> <p>Fast-flowing <span class="hlt">ice</span> streams transport <span class="hlt">ice</span> from the interior of West Antarctica to the ocean, and fluctuations in their activity control the <span class="hlt">mass</span> balance of the <span class="hlt">ice</span> sheet. The <span class="hlt">mass</span> balance of the Ross Sea sector of the West Antarctic <span class="hlt">ice</span> sheet is now positive--that is, it is growing--mainly because one of the <span class="hlt">ice</span> streams (<span class="hlt">ice</span> stream C) slowed down about 150 years ago. Here we present evidence from both surface measurements and remote sensing that demonstrates the highly dynamic nature of the Ross drainage system. We show that the flow in an area that once discharged into <span class="hlt">ice</span> stream C has changed direction, now draining into the Whillans <span class="hlt">ice</span> stream (formerly <span class="hlt">ice</span> stream B). This switch in flow direction is a result of continuing thinning of the Whillans <span class="hlt">ice</span> stream and recent thickening of <span class="hlt">ice</span> stream C. Further abrupt reorganization of the activity and configuration of the <span class="hlt">ice</span> streams over short timescales is to be expected in the future as the surface topography of the <span class="hlt">ice</span> sheet responds to the combined effects of internal dynamics and long-term climate change. We suggest that caution is needed when using observations of short-term <span class="hlt">mass</span> changes to draw conclusions about the large-scale <span class="hlt">mass</span> balance of the <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913594F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913594F"><span>Surface elevation change over the Patagonia <span class="hlt">Ice</span> Fields using CryoSat-2 swath altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Foresta, Luca; Gourmelen, Noel; José Escorihuela, MarÍa; Garcia Mondejar, Albert; Wuite, Jan; Shepherd, Andrew; Roca, Mònica; Nagler, Thomas; Brockley, David; Baker, Steven; Nienow, Pete</p> <p>2017-04-01</p> <p>Satellite altimetry has been traditionally used in the past few decades to infer elevation of land <span class="hlt">ice</span>, quantify changes in <span class="hlt">ice</span> topography and infer <span class="hlt">mass</span> balance estimates over large and remote areas such as the Greenland and Antarctic <span class="hlt">ice</span> sheets. Radar Altimetry (RA) is particularly well suited to this task due to its all-weather year-round capability of observing the <span class="hlt">ice</span> surface. However, monitoring of <span class="hlt">ice</span> caps (area < 104 km^2) as well as mountain glaciers has proven more challenging. The large footprint of a conventional radar altimeter and relatively coarse ground track coverage are less suited to monitoring comparatively small regions with complex topography, so that <span class="hlt">mass</span> balance estimates from RA rely on extrapolation methods to regionalize elevation change. Since 2010, the European Space Agency's CryoSat-2 (CS-2) satellite has collected <span class="hlt">ice</span> elevation measurements over <span class="hlt">ice</span> caps with its novel radar altimeter. CS-2 provides higher <span class="hlt">density</span> of observations w.r.t. previous satellite altimeters, reduces the along-track footprint using Synthetic Aperture Radar (SAR) processing and locates the across-track origin of a surface reflector in the presence of a slope with SAR Interferometry (SARIn). Here, we exploit CS-2 as a swath altimeter [Hawley et al., 2009; Gray et al., 2013; Christie et al., 2016; Ignéczi et al., 2016, Foresta et al., 2016] over the Southern and Northern Patagonian <span class="hlt">Ice</span> Fields (SPI and NPI, respectively). The SPI and NPI are the two largest <span class="hlt">ice</span> <span class="hlt">masses</span> in the southern hemisphere outside of Antarctica and are thinning very rapidly in recent decades [e.g Rignot et al., 2003; Willis et al, 2012]. However, studies of surface, volume and <span class="hlt">mass</span> change in the literature, covering the entire SPI and NPI, are limited in number due to their remoteness, extremely complex topography and wide range of slopes. In this work, we present rates of surface elevation change for five glaciological years between 2011-2016 using swath-processed CS-2 SARIn heights and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..93f4204H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93f4204H"><span>Dynamics anomaly in high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> between 0.7 and 1.1 GPa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Handle, Philip H.; Loerting, Thomas</p> <p>2016-02-01</p> <p>We studied high-<span class="hlt">density</span> amorphous <span class="hlt">ices</span> between 0.004 and 1.6 GPa by isobaric in situ volumetry and by subsequent ex situ x-ray diffraction and differential scanning calorimetry at 1 bar. Our observations indicate two processes, namely, relaxation in the amorphous matrix and crystallization, taking place at well-separated time scales. For this reason, we are able to report rate constants of crystallization kX and glass-transition temperatures Tg in an unprecedented pressure range. Tg's agree within ±3 K with earlier work in the small pressure range where there is overlap. Both Tg and kX show a pressure anomaly between 0.7 and 1.1 GPa, namely, a kX minimum and a Tg maximum. This anomalous pressure dependence suggests a continuous phase transition from high- (HDA) to very-high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (VHDA) and faster hydrogen bond dynamics in VHDA. We speculate this phenomenology can be rationalized by invoking the crossing of a Widom line between 0.7 and 1.1 GPa emanating from a low-lying HDA-VHDA critical point. Furthermore, we interpret the volumetric relaxation of the amorphous matrix to be accompanied by viscosity change to explain the findings such that the liquid state can be accessed prior to the crystallization temperature TX at <0.4 GPa and >0.8 GPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890042500&hterms=gravitational+lensing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgravitational%2Blensing','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890042500&hterms=gravitational+lensing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgravitational%2Blensing"><span>Gravitational lensing by a smoothly variable surface <span class="hlt">mass</span> <span class="hlt">density</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paczynski, Bohdan; Wambsganss, Joachim</p> <p>1989-01-01</p> <p>The statistical properties of gravitational lensing due to smooth but nonuniform distributions of matter are considered. It is found that a majority of triple images had a parity characteristic for 'shear-induced' lensing. Almost all cases of triple or multiple imaging were associated with large surface <span class="hlt">density</span> enhancements, and lensing objects were present between the images. Thus, the observed gravitational lens candidates for which no lensing object has been detected between the images are unlikely to be a result of asymmetric distribution of <span class="hlt">mass</span> external to the image circle. In a model with smoothly variable surface <span class="hlt">mass</span> <span class="hlt">density</span>, moderately and highly amplified images tended to be single rather than multiple. An opposite trend was found in models which had singularities in the surface <span class="hlt">mass</span> distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C13G..05W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C13G..05W"><span>Antarctic <span class="hlt">ice</span> discharge due to warm water intrusion into shelf cavities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winkelmann, R.; Reese, R.; Albrecht, T.; Mengel, M.; Asay-Davis, X.</p> <p>2017-12-01</p> <p>Ocean-induced melting below <span class="hlt">ice</span> shelves is the dominant driver for <span class="hlt">mass</span> loss from the Antarctic <span class="hlt">Ice</span> Sheet at present. Observations show that many Antarctic <span class="hlt">ice</span> shelves are thinning which reduces their buttressing potential and can lead to increased <span class="hlt">ice</span> discharge from the glaciers upstream. Melt rates from Antarctic <span class="hlt">ice</span> shelves are determined by the temperature and salinity of the ambient ocean. In many parts, <span class="hlt">ice</span> shelves are shielded by clearly defined <span class="hlt">density</span> fronts which keep relatively warm Northern water from entering the cavity underneath the <span class="hlt">ice</span> shelves. Projections show that a redirection of coastal currents might allow these warmer waters to intrude into <span class="hlt">ice</span> shelf cavities, for instance in the Weddell Sea, and thereby cause a strong increase in sub-shelf melt rates. Using the Potsdam <span class="hlt">Ice</span>-shelf Cavity mOdel (PICO), we assess how such a change would influence the dynamic <span class="hlt">ice</span> loss from Antarctica. PICO is implemented as part of the Parallel <span class="hlt">Ice</span> Sheet Model (PISM) and mimics the vertical overturning circulation in <span class="hlt">ice</span>-shelf cavities. The model is capable of capturing the wide range of melt rates currently observed for Antarctic <span class="hlt">ice</span> shelves and reproduces the typical pattern of comparably high melting near the grounding line and lower melting or refreezing towards the calving front. Based on regional observations of ocean temperatures, we use PISM-PICO to estimate an upper limit for <span class="hlt">ice</span> discharge resulting from the potential erosion of ocean fronts around Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AcO....63...16D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AcO....63...16D"><span><span class="hlt">Density</span>-body <span class="hlt">mass</span> relationships: Inconsistent intercontinental patterns among termite feeding-groups</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dahlsjö, Cecilia A. L.; Parr, Catherine L.; Malhi, Yadvinder; Meir, Patrick; Rahman, Homathevi; Eggleton, Paul</p> <p>2015-02-01</p> <p>Allometric relationships are useful for estimating and understanding resource distribution in assemblages with species of different <span class="hlt">masses</span>. Damuth's law states that body <span class="hlt">mass</span> scales with population <span class="hlt">density</span> as M-0.75, where M is body <span class="hlt">mass</span> and -0.75 is the slope. In this study we used Damuth's law (M-0.75) as a null hypothesis to examine the relationship between body <span class="hlt">mass</span> and population <span class="hlt">density</span> for termite feeding-groups in three different countries and regions (Cameroon, West Africa; Peru South America; and Malaysia SE Asia). We found that none of the feeding-groups had a relationship where M-0.75 while the data suggested that population <span class="hlt">density</span>-body <span class="hlt">mass</span> relationships for true soil-feeding termites in Cameroon (M2.7) and wood-feeding termites in Peru (M1.5) were significantly different from the expected values given by Damuth's law. The dominance of large-bodied true soil-feeding termites in Cameroon and the absence of fungus-growing termites from Peru suggest that these allometric patterns are due to heterogeneities in termite biogeographical evolution. Additionally, as these feeding-groups have higher population <span class="hlt">density</span> than expected by their body <span class="hlt">masses</span> it may be suggested that they also have a higher energy throughput than expected. The results presented here may be used to gain further understanding of resource distribution among termite feeding-groups across regions and an insight into the importance of evolutionary history and biogeography on allometric patterns. Further understanding of population <span class="hlt">density</span>-body <span class="hlt">mass</span> relationships in termite feeding-groups may also improve understanding of the role these feeding-groups play in ecosystem processes in different regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.6008T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.6008T"><span>Influences of Ocean Thermohaline Stratification on Arctic Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toole, J. M.; Timmermans, M.-L.; Perovich, D. K.; Krishfield, R. A.; Proshutinsky, A.; Richter-Menge, J. A.</p> <p>2009-04-01</p> <p>The Arctic Ocean's surface mixed layer constitutes the dynamical and thermodynamical link between the sea <span class="hlt">ice</span> and the underlying waters. Wind stress, acting directly on the surface mixed layer or via wind-forced <span class="hlt">ice</span> motion, produce surface currents that can in turn drive deep ocean flow. Mixed layer temperature is intimately related to basal sea <span class="hlt">ice</span> growth and melting. Heat fluxes into or out of the surface mixed layer can occur at both its upper and lower interfaces: the former via air-sea exchange at leads and conduction through the <span class="hlt">ice</span>, the latter via turbulent mixing and entrainment at the layer base. Variations in Arctic Ocean mixed layer properties are documented based on more than 16,000 temperature and salinity profiles acquired by <span class="hlt">Ice</span>-Tethered Profilers since summer 2004 and analyzed in conjunction with sea <span class="hlt">ice</span> observations from <span class="hlt">Ice</span> <span class="hlt">Mass</span> Balance Buoys and atmospheric heat flux estimates. Guidance interpreting the observations is provided by a one-dimensional ocean mixed layer model. The study focuses attention on the very strong <span class="hlt">density</span> stratification about the mixed layer base in the Arctic that, in regions of sea <span class="hlt">ice</span> melting, is increasing with time. The intense stratification greatly impedes mixed layer deepening by vertical convection and shear mixing, and thus limits the flux of deep ocean heat to the surface that could influence sea <span class="hlt">ice</span> growth/decay. Consistent with previous work, this study demonstrates that the Arctic sea <span class="hlt">ice</span> is most sensitive to changes in ocean mixed layer heat resulting from fluxes across its upper (air-sea and/or <span class="hlt">ice</span>-water) interface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatGe...8..534U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatGe...8..534U"><span>Laurentide <span class="hlt">ice</span>-sheet instability during the last deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ullman, David J.; Carlson, Anders E.; Anslow, Faron S.; Legrande, Allegra N.; Licciardi, Joseph M.</p> <p>2015-07-01</p> <p>Changes in the amount of summer incoming solar radiation (insolation) reaching the Northern Hemisphere are the underlying pacemaker of glacial cycles. However, not all rises in boreal summer insolation over the past 800,000 years resulted in deglaciation to present-day <span class="hlt">ice</span> volumes, suggesting that there may be a climatic threshold for the disappearance of land-based <span class="hlt">ice</span>. Here we assess the surface <span class="hlt">mass</span> balance stability of the Laurentide <span class="hlt">ice</span> sheet--the largest glacial <span class="hlt">ice</span> <span class="hlt">mass</span> in the Northern Hemisphere--during the last deglaciation (24,000 to 9,000 years ago). We run a surface energy balance model with climate data from simulations with a fully coupled atmosphere-ocean general circulation model for key time slices during the last deglaciation. We find that the surface <span class="hlt">mass</span> balance of the Laurentide <span class="hlt">ice</span> sheet was positive throughout much of the deglaciation, and suggest that dynamic discharge was mainly responsible for <span class="hlt">mass</span> loss during this time. Total surface <span class="hlt">mass</span> balance became negative only in the early Holocene, indicating the transition to a new state where <span class="hlt">ice</span> loss occurred primarily by surface ablation. We conclude that the Laurentide <span class="hlt">ice</span> sheet remained a viable <span class="hlt">ice</span> sheet before the Holocene and began to fully deglaciate only once summer temperatures and radiative forcing over the <span class="hlt">ice</span> sheet increased by 6-7 °C and 16-20 W m-2, respectively, relative to full glacial conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvL.119m6002M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvL.119m6002M"><span>Large-Scale Structure and Hyperuniformity of Amorphous <span class="hlt">Ices</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martelli, Fausto; Torquato, Salvatore; Giovambattista, Nicolas; Car, Roberto</p> <p>2017-09-01</p> <p>We investigate the large-scale structure of amorphous <span class="hlt">ices</span> and transitions between their different forms by quantifying their large-scale <span class="hlt">density</span> fluctuations. Specifically, we simulate the isothermal compression of low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (LDA) and hexagonal <span class="hlt">ice</span> to produce high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA). Both HDA and LDA are nearly hyperuniform; i.e., they are characterized by an anomalous suppression of large-scale <span class="hlt">density</span> fluctuations. By contrast, in correspondence with the nonequilibrium phase transitions to HDA, the presence of structural heterogeneities strongly suppresses the hyperuniformity and the system becomes hyposurficial (devoid of "surface-area fluctuations"). Our investigation challenges the largely accepted "frozen-liquid" picture, which views glasses as structurally arrested liquids. Beyond implications for water, our findings enrich our understanding of pressure-induced structural transformations in glasses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhFl...30b7101J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhFl...30b7101J"><span>Mixed <span class="hlt">ice</span> accretion on aircraft wings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Janjua, Zaid A.; Turnbull, Barbara; Hibberd, Stephen; Choi, Kwing-So</p> <p>2018-02-01</p> <p><span class="hlt">Ice</span> accretion is a problematic natural phenomenon that affects a wide range of engineering applications including power cables, radio masts, and wind turbines. Accretion on aircraft wings occurs when supercooled water droplets freeze instantaneously on impact to form rime <span class="hlt">ice</span> or runback as water along the wing to form glaze <span class="hlt">ice</span>. Most models to date have ignored the accretion of mixed <span class="hlt">ice</span>, which is a combination of rime and glaze. A parameter we term the "freezing fraction" is defined as the fraction of a supercooled droplet that freezes on impact with the top surface of the accretion <span class="hlt">ice</span> to explore the concept of mixed <span class="hlt">ice</span> accretion. Additionally we consider different "packing <span class="hlt">densities</span>" of rime <span class="hlt">ice</span>, mimicking the different bulk rime <span class="hlt">densities</span> observed in nature. <span class="hlt">Ice</span> accretion is considered in four stages: rime, primary mixed, secondary mixed, and glaze <span class="hlt">ice</span>. Predictions match with existing models and experimental data in the limiting rime and glaze cases. The mixed <span class="hlt">ice</span> formulation however provides additional insight into the composition of the overall <span class="hlt">ice</span> structure, which ultimately influences adhesion and <span class="hlt">ice</span> thickness, and shows that for similar atmospheric parameter ranges, this simple mixed <span class="hlt">ice</span> description leads to very different accretion rates. A simple one-dimensional energy balance was solved to show how this freezing fraction parameter increases with decrease in atmospheric temperature, with lower freezing fraction promoting glaze <span class="hlt">ice</span> accretion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA41B2618H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA41B2618H"><span>Scale Sizes of High-Latitude Neutral <span class="hlt">Mass</span> <span class="hlt">Density</span> Perturbations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, C. Y.; Huang, Y.; Su, Y. J.; Huang, T.; Sutton, E. K.</p> <p>2017-12-01</p> <p>In a statistical study of neutral <span class="hlt">mass</span> <span class="hlt">density</span> maxima, we found for a select interval, that 57% of the maxima have correlated field-aligned current (FAC) signatures, indicative of localized Ohmic heating. However the remaining 43% do not, and we suggested that these maxima may be due to gravity waves generated by neutral heating. We follow up on this study by an investigation into the spatial scale sizes of the <span class="hlt">mass</span> <span class="hlt">density</span> maxima using high-resolution neutral <span class="hlt">density</span> and FAC data from CHAMP, when the satellite is in conjunction with DMSP, which provides the corresponding ion drift velocity, particle precipitation and Poynting flux. The study shows the average scale sizes of the perturbations due to J x B heating, as well as the sizes of the waves generated by Joule heating.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900007359','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900007359"><span>Neptune's Triton: A moon rich in dry <span class="hlt">ice</span> and carbon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Prentice, A. J. R.</p> <p>1989-01-01</p> <p>The encounter of the spacecraft Voyager 2 with Neptune and its large satellite Triton in August 1989 will provide a crucial test of ideas regarding the origin and chemical composition of the outer solar system. In this pre-encounter publication, the possibility is quantified that Titron is a captured moon which, like Pluto and Charon, originally condensed as a major planetesimal within the gas ring that was shed by the contracting protosolar cloud at Neptune's orbit. Ideas of supersonic convective turbulence are used to compute the gas pressure, temperature and rat of catalytic synthesis of CH4, CO2, and C(s) within the protosolar cloud, assuming that all C is initially present as CO. The calculations lead to a unique composition for Triton, Pluto, Charon: each body consists of, by <span class="hlt">mass</span>, 18 1/2 percent solid CO2 <span class="hlt">ice</span>, 4 percent graphite, 1/2 percent CH4 <span class="hlt">ice</span>, 29 percent methanated water <span class="hlt">ice</span> and 48 percent of anhydrous rock. This mix has a <span class="hlt">density</span> consistent with that of the Pluto-Charon system and yields a predicted mean <span class="hlt">density</span> for Triton of 2.20 + or - 0.5 g/cu cm, for satellite radius equal to 1,750 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170007301','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170007301"><span>Evaluation of Alternative Altitude Scaling Methods for Thermal <span class="hlt">Ice</span> Protection System in NASA <span class="hlt">Icing</span> Research Tunnel</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, Sam; Addy, Harold; Broeren, Andy P.; Orchard, David M.</p> <p>2017-01-01</p> <p>A test was conducted at NASA <span class="hlt">Icing</span> Research Tunnel to evaluate altitude scaling methods for thermal <span class="hlt">ice</span> protection system. Two scaling methods based on Weber number were compared against a method based on the Reynolds number. The results generally agreed with the previous set of tests conducted in NRCC Altitude <span class="hlt">Icing</span> Wind Tunnel. The Weber number based scaling methods resulted in smaller runback <span class="hlt">ice</span> <span class="hlt">mass</span> than the Reynolds number based scaling method. The <span class="hlt">ice</span> accretions from the Weber number based scaling method also formed farther upstream. However there were large differences in the accreted <span class="hlt">ice</span> <span class="hlt">mass</span> between the two Weber number based scaling methods. The difference became greater when the speed was increased. This indicated that there may be some Reynolds number effects that isnt fully accounted for and warrants further study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990071137&hterms=ice+mechanics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dice%2Bmechanics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990071137&hterms=ice+mechanics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dice%2Bmechanics"><span><span class="hlt">Ice</span> Flow in the North East Greenland <span class="hlt">Ice</span> Stream</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug</p> <p>1999-01-01</p> <p>Early observations with ERS-1 SAR image data revealed a large <span class="hlt">ice</span> stream in North East Greenland (Fahnestock 1993). The <span class="hlt">ice</span> stream has a number of the characteristics of the more closely studied <span class="hlt">ice</span> streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the <span class="hlt">ice</span> divide and the evolution of its flow pattern, however, make this <span class="hlt">ice</span> stream unique. These features can be seen in the balance velocities for the <span class="hlt">ice</span> stream (Joughin 1997) and its outlets. The <span class="hlt">ice</span> stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the <span class="hlt">ice</span> flow in the northeast Greenland <span class="hlt">ice</span> stream and its outlet glaciers in order to assess their impact on the past, present, and future <span class="hlt">mass</span> balance of the <span class="hlt">ice</span> sheet. We will accomplish these goals using a combination of remotely sensed data and <span class="hlt">ice</span> sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire <span class="hlt">ice</span> stream. We are in the process of developing methods to use these data in conjunction with existing <span class="hlt">ice</span> sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic <span class="hlt">ice</span> streams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvD..93b5022Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvD..93b5022Q"><span>Quark matter at high <span class="hlt">density</span> based on an extended confined isospin-<span class="hlt">density</span>-dependent <span class="hlt">mass</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qauli, A. I.; Sulaksono, A.</p> <p>2016-01-01</p> <p>We investigate the effect of the inclusion of relativistic Coulomb terms in a confined-isospin-<span class="hlt">density-dependent-mass</span> (CIDDM) model of strange quark matter (SQM). We found that if we include the Coulomb term in scalar <span class="hlt">density</span> form, the SQM equation of state (EOS) at high <span class="hlt">densities</span> is stiffer but if we include the Coulomb term in vector <span class="hlt">density</span> form it is softer than that of the standard CIDDM model. We also investigate systematically the role of each term of the extended CIDDM model. Compared with what was reported by Chu and Chen [Astrophys. J. 780, 135 (2014)], we found the stiffness of SQM EOS is controlled by the interplay among the oscillator harmonic, isospin asymmetry and Coulomb contributions depending on the parameter's range of these terms. We have found that the absolute stable condition of SQM and the <span class="hlt">mass</span> of 2 M⊙ pulsars can constrain the parameter of oscillator harmonic κ1≈0.53 in the case the Coulomb term is excluded. If the Coulomb term is included, for the models with their parameters are consistent with SQM absolute stability condition, the 2.0 M⊙ constraint more prefers the maximum <span class="hlt">mass</span> prediction of the model with the scalar Coulomb term than that of the model with the vector Coulomb term. On the contrary, the high <span class="hlt">densities</span> EOS predicted by the model with the vector Coulomb is more compatible with the recent perturbative quantum chromodynamics result [1] than that predicted by the model with the scalar Coulomb. Furthermore, we also observed the quark composition in a very high <span class="hlt">density</span> region depends quite sensitively on the kind of Coulomb term used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C11A0533C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C11A0533C"><span>From Outlet Glacier Changes to <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> Balance - Evolution of Greenland <span class="hlt">Ice</span> Sheet from Laser Altimetry Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Csatho, B. M.; Schenk, A.; Nagarajan, S.; Babonis, G. S.</p> <p>2010-12-01</p> <p>Investigations of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance and the changing dynamics of outlet glaciers have been hampered by the lack of comprehensive data. In recent years, this situation has been remedied. Satellite laser altimetry data from the <span class="hlt">Ice</span> Cloud and land Elevation Satellite mission (ICESat), combined with airborne laser altimetry, provide accurate measurements of surface elevation changes, and surface velocities derived from various satellite platforms yield crucial information on changing glacier dynamics. Taken together, a rich and diverse data set is emerging that allows for characterizing the spatial and temporal evolution of <span class="hlt">ice</span> sheets and outlet glaciers. In particular, it enables quantitative studies of outlet glaciers undergoing rapid and complex changes. Although airborne and laser altimetry have been providing precise measurements of <span class="hlt">ice</span> sheet topography since the early 1990s, determining detailed and accurate spatial and temporal distribution of surface changes remains a challenging problem. We have developed a new, comprehensive method, called Surface Elevation Reconstruction And Change detection (SERAC), which estimates surface changes by a simultaneous reconstruction of surface topography from fused multisensor data. The mathematical model is based on the assumption that for a small surface area, only the absolute elevation changes over time but not the shape of the surface patch. Therefore, laser points of all time epochs contribute to the shape parameters; points of each time period determine the absolute elevation of the surface patch at that period. This method provides high-resolution surface topography, precise changes and a rigorous error estimate of the quantities. By using SERAC we combined ICESat and ATM laser altimetry data to determine the evolution of surface change rates of the whole Greenland <span class="hlt">Ice</span> Sheet between 2003 and 2009 on a high-resolution grid. Our reconstruction, consistent with GRACE results, shows <span class="hlt">ice</span> sheet thinning propagating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7488S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7488S"><span>Integrated firn elevation change model for glaciers and <span class="hlt">ice</span> caps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saß, Björn; Sauter, Tobias; Braun, Matthias</p> <p>2016-04-01</p> <p>We present the development of a firn compaction model in order to improve the volume to <span class="hlt">mass</span> conversion of geodetic glacier <span class="hlt">mass</span> balance measurements. The model is applied on the Arctic <span class="hlt">ice</span> cap Vestfonna. Vestfonna is located on the island Nordaustlandet in the north east of Svalbard. Vestfonna covers about 2400 km² and has a dome like shape with well-defined outlet glaciers. Elevation and volume changes measured by e.g. satellite techniques are becoming more and more popular. They are carried out over observation periods of variable length and often covering different meteorological and snow hydrological regimes. The elevation change measurements compose of various components including dynamic adjustments, firn compaction and <span class="hlt">mass</span> loss by downwasting. Currently, geodetic glacier <span class="hlt">mass</span> balances are frequently converted from elevation change measurements using a constant conversion factor of 850 kg m-³ or the <span class="hlt">density</span> of <span class="hlt">ice</span> (917 kg m-³) for entire glacier basins. However, the natural conditions are rarely that static. Other studies used constant <span class="hlt">densities</span> for the ablation (900 kg m-³) and accumulation (600 kg m-³) areas, whereby <span class="hlt">density</span> variations with varying meteorological and climate conditions are not considered. Hence, each approach bears additional uncertainties from the volume to <span class="hlt">mass</span> conversion that are strongly affected by the type and timing of the repeat measurements. We link and adapt existing models of surface energy balance, accumulation and snow and firn processes in order to improve the volume to <span class="hlt">mass</span> conversion by considering the firn compaction component. Energy exchange at the surface is computed by a surface energy balance approach and driven by meteorological variables like incoming short-wave radiation, air temperature, relative humidity, air pressure, wind speed, all-phase precipitation, and cloud cover fraction. Snow and firn processes are addressed by a coupled subsurface model, implemented with a non-equidistant layer discretisation. On</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21394250-halo-mass-function-conditioned-density-from-millennium-simulation-insights-missing-baryons-galaxy-mass-functions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21394250-halo-mass-function-conditioned-density-from-millennium-simulation-insights-missing-baryons-galaxy-mass-functions"><span>THE HALO <span class="hlt">MASS</span> FUNCTION CONDITIONED ON <span class="hlt">DENSITY</span> FROM THE MILLENNIUM SIMULATION: INSIGHTS INTO MISSING BARYONS AND GALAXY <span class="hlt">MASS</span> FUNCTIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Faltenbacher, A.; Finoguenov, A.; Drory, N.</p> <p>2010-03-20</p> <p>The baryon content of high-<span class="hlt">density</span> regions in the universe is relevant to two critical unanswered questions: the workings of nurture effects on galaxies and the whereabouts of the missing baryons. In this paper, we analyze the distribution of dark matter and semianalytical galaxies in the Millennium Simulation to investigate these problems. Applying the same <span class="hlt">density</span> field reconstruction schemes as used for the overall matter distribution to the matter locked in halos, we study the <span class="hlt">mass</span> contribution of halos to the total <span class="hlt">mass</span> budget at various background field <span class="hlt">densities</span>, i.e., the conditional halo <span class="hlt">mass</span> function. In this context, we present amore » simple fitting formula for the cumulative <span class="hlt">mass</span> function accurate to {approx}<5% for halo <span class="hlt">masses</span> between 10{sup 10} and 10{sup 15} h {sup -1} M{sub sun}. We find that in dense environments the halo <span class="hlt">mass</span> function becomes top heavy and present corresponding fitting formulae for different redshifts. We demonstrate that the major fraction of matter in high-<span class="hlt">density</span> fields is associated with galaxy groups. Since current X-ray surveys are able to nearly recover the universal baryon fraction within groups, our results indicate that the major part of the so-far undetected warm-hot intergalactic medium resides in low-<span class="hlt">density</span> regions. Similarly, we show that the differences in galaxy <span class="hlt">mass</span> functions with environment seen in observed and simulated data stem predominantly from differences in the <span class="hlt">mass</span> distribution of halos. In particular, the hump in the galaxy <span class="hlt">mass</span> function is associated with the central group galaxies, and the bimodality observed in the galaxy <span class="hlt">mass</span> function is therefore interpreted as that of central galaxies versus satellites.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeCoA..73.4423H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeCoA..73.4423H"><span>A surface structural model for ferrihydrite I: Sites related to primary charge, molar <span class="hlt">mass</span>, and <span class="hlt">mass</span> <span class="hlt">density</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hiemstra, Tjisse; Van Riemsdijk, Willem H.</p> <p>2009-08-01</p> <p>A multisite surface complexation (MUSIC) model for ferrihydrite (Fh) has been developed. The surface structure and composition of Fh nanoparticles are described in relation to ion binding and surface charge development. The site <span class="hlt">densities</span> of the various reactive surface groups, the molar <span class="hlt">mass</span>, the <span class="hlt">mass</span> <span class="hlt">density</span>, the specific surface area, and the particle size are quantified. As derived theoretically, molecular <span class="hlt">mass</span> and <span class="hlt">mass</span> <span class="hlt">density</span> of nanoparticles will depend on the types of surface groups and the corresponding site <span class="hlt">densities</span> and will vary with particle size and surface area because of a relatively large contribution of the surface groups in comparison to the mineral core of nanoparticles. The nano-sized (˜2.6 nm) particles of freshly prepared 2-line Fh as a whole have an increased molar <span class="hlt">mass</span> of M ˜ 101 ± 2 g/mol Fe, a reduced <span class="hlt">mass</span> <span class="hlt">density</span> of ˜3.5 ± 0.1 g/cm 3, both relatively to the mineral core. The specific surface area is ˜650 m 2/g. Six-line Fh (5-6 nm) has a molar <span class="hlt">mass</span> of M ˜ 94 ± 2 g/mol, a <span class="hlt">mass</span> <span class="hlt">density</span> of ˜3.9 ± 0.1 g/cm 3, and a surface area of ˜280 ± 30 m 2/g. Data analysis shows that the mineral core of Fh has an average chemical composition very close to FeOOH with M ˜ 89 g/mol. The mineral core has a <span class="hlt">mass</span> <span class="hlt">density</span> around ˜4.15 ± 0.1 g/cm 3, which is between that of feroxyhyte, goethite, and lepidocrocite. These results can be used to constrain structural models for Fh. Singly-coordinated surface groups dominate the surface of ferrihydrite (˜6.0 ± 0.5 nm -2). These groups can be present in two structural configurations. In pairs, the groups either form the edge of a single Fe-octahedron (˜2.5 nm -2) or are present at a single corner (˜3.5 nm -2) of two adjacent Fe octahedra. These configurations can form bidentate surface complexes by edge- and double-corner sharing, respectively, and may therefore respond differently to the binding of ions such as uranyl, carbonate, arsenite, phosphate, and others. The relatively low PZC of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C41D..02R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C41D..02R"><span><span class="hlt">Ice</span>-shelf melting around Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.; Jacobs, S.</p> <p>2008-12-01</p> <p>The traditional view on the <span class="hlt">mass</span> balance of Antarctic <span class="hlt">ice</span> shelves is that they loose <span class="hlt">mass</span> principally from iceberg calving with bottom melting a much lower contributing factor. Because <span class="hlt">ice</span> shelves are now known to play a fundamental role in <span class="hlt">ice</span> sheet evolution, it is important to re-evaluate their wastage processes from a circumpolar perspective using a combination of remote sensing techniques. We present area average rates deduced from grounding line discharge, snow accumulation, firn depth correction and <span class="hlt">ice</span> shelf topography. We find that <span class="hlt">ice</span> shelf melting accounts for roughly half of <span class="hlt">ice</span>-shelf ablation, with a total melt water production of 1027 Gt/yr. The attrition fraction due to in-situ melting varies from 9 to 90 percent around Antarctica. High melt producers include the Ronne, Ross, Getz, Totten, Amery, George VI, Pine Island, Abbot, Dotson/Crosson, Shackleton, Thwaites and Moscow University <span class="hlt">Ice</span> Shelves. Low producers include the Larsen C, Princess Astrid and Ragnhild coast, Fimbul, Brunt and Filchner. Correlation between melt water production and grounding line discharge is low (R2 = 0.65). Correlation with thermal ocean forcing from the ocean are highest in the northern parts of West Antarctica where regressions yield R2 of 0.93-0.97. Melt rates in the Amundsen Sea exhibit a quadratic sensitivity to thermal ocean forcing. We conclude that <span class="hlt">ice</span> shelf melting plays a dominant role in <span class="hlt">ice</span> shelf <span class="hlt">mass</span> balance, with a potential to change rapidly in response to altered ocean heat transport onto the Antarctic continental shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A12C..03C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A12C..03C"><span>Advances in Understanding the Role of Aerosols on <span class="hlt">Ice</span> Clouds from the Fifth International <span class="hlt">Ice</span> Nucleation (FIN) Workshops</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cziczo, D. J.; Moehler, O.; DeMott, P. J.</p> <p>2015-12-01</p> <p>The relationship of ambient aerosol particles to the formation of <span class="hlt">ice</span>-containing clouds is one of the largest uncertainties in understanding climate. This is due to several poorly understood processes including the microphysics of how particles nucleate <span class="hlt">ice</span>, the number of effective heterogeneous <span class="hlt">ice</span> nuclei and their atmospheric distribution, the role of anthropogenic activities in producing or changing the behavior of <span class="hlt">ice</span> forming particles and the interplay between effective heterogeneous <span class="hlt">ice</span> nuclei and homogeneous <span class="hlt">ice</span> formation. Our team recently completed a three-part international workshop to improve our understanding of atmospheric <span class="hlt">ice</span> formation. Termed the Fifth International <span class="hlt">Ice</span> Nucleation (FIN) Workshops, our motivation was the limited number of measurements and a lack of understanding of how to compare data acquired by different groups. The first activity, termed FIN1, addressed the characterization of <span class="hlt">ice</span> nucleating particle size, number and chemical composition. FIN2 addressed the determination of <span class="hlt">ice</span> nucleating particle number <span class="hlt">density</span>. Groups modeling <span class="hlt">ice</span> nucleation joined FIN2 to provide insight on measurements critically needed to model atmospheric <span class="hlt">ice</span> nucleation and to understand the performance of <span class="hlt">ice</span> chambers. FIN1 and FIN2 took place at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) chamber at the Karlsruhe Institute of Technology. A particular emphasis of FIN1 and FIN2 was the use of 'blind' intercomparisons using a highly characterized, but unknown to the instrument operators, aerosol sample. The third activity, FIN3, took place at the Desert Research Institute's Storm Peak Laboratory (SPL). A high elevation site not subject to local emissions, SPL allowed for a comparison of <span class="hlt">ice</span> chambers and subsequent analysis of the <span class="hlt">ice</span> residuals under the challenging conditions of low particle loading, temperature and pressure found in the atmosphere. The presentation focuses on the improvement in understanding how <span class="hlt">mass</span> spectra from different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22611863','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22611863"><span>A Bayesian hierarchical model of Antarctic fur seal foraging and pup growth related to sea <span class="hlt">ice</span> and prey abundance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hiruki-Raring, Lisa M; Ver Hoef, Jay M; Boveng, Peter L; Bengtson, John L</p> <p>2012-03-01</p> <p>We created a Bayesian hierarchical model (BHM) to investigate ecosystem relationships between the physical ecosystem (sea <span class="hlt">ice</span> extent), a prey measure (krill <span class="hlt">density</span>), predator behaviors (diving and foraging effort of female Antarctic fur seals, Arctocephalus gazella, with pups) and predator characteristics (<span class="hlt">mass</span> of maternal fur seals and pups). We collected data on Antarctic fur seals from 1987/1988 to 1994/1995 at Seal Island, Antarctica. The BHM allowed us to link together predators and prey into a model that uses all the data efficiently and accounts for major sources of uncertainty. Based on the literature, we made hypotheses about the relationships in the model, which we compared with the model outcome after fitting the BHM. For each BHM parameter, we calculated the mean of the posterior <span class="hlt">density</span> and the 95% credible interval. Our model confirmed others' findings that increased sea <span class="hlt">ice</span> was related to increased krill <span class="hlt">density</span>. Higher krill <span class="hlt">density</span> led to reduced dive intensity of maternal fur seals, as measured by dive depth and duration, and to less time spent foraging by maternal fur seals. Heavier maternal fur seals and lower maternal foraging effort resulted in heavier pups at 22 d. No relationship was found between krill <span class="hlt">density</span> and maternal <span class="hlt">mass</span>, or between maternal <span class="hlt">mass</span> and foraging effort on pup growth rates between 22 and 85 days of age. Maternal <span class="hlt">mass</span> may have reflected environmental conditions prior to the pup provisioning season, rather than summer prey <span class="hlt">densities</span>. Maternal <span class="hlt">mass</span> and foraging effort were not related to pup growth rates between 22 and 85 d, possibly indicating that food was not limiting, food sources other than krill were being used, or differences occurred before pups reached age 22 d.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1352361-present-day-future-antarctic-ice-sheet-climate-surface-mass-balance-community-earth-system-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1352361-present-day-future-antarctic-ice-sheet-climate-surface-mass-balance-community-earth-system-model"><span>Present-day and future Antarctic <span class="hlt">ice</span> sheet climate and surface <span class="hlt">mass</span> balance in the Community Earth System Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Lenaerts, Jan T. M.; Vizcaino, Miren; Fyke, Jeremy Garmeson; ...</p> <p>2016-02-01</p> <p>Here, we present climate and surface <span class="hlt">mass</span> balance (SMB) of the Antarctic <span class="hlt">ice</span> sheet (AIS) as simulated by the global, coupled ocean–atmosphere–land Community Earth System Model (CESM) with a horizontal resolution of ~1° in the past, present and future (1850–2100). CESM correctly simulates present-day Antarctic sea <span class="hlt">ice</span> extent, large-scale atmospheric circulation and near-surface climate, but fails to simulate the recent expansion of Antarctic sea <span class="hlt">ice</span>. The present-day Antarctic <span class="hlt">ice</span> sheet SMB equals 2280 ± 131Gtyear –1, which concurs with existing independent estimates of AIS SMB. When forced by two CMIP5 climate change scenarios (high mitigation scenario RCP2.6 and high-emission scenariomore » RCP8.5), CESM projects an increase of Antarctic <span class="hlt">ice</span> sheet SMB of about 70 Gtyear –1 per degree warming. This increase is driven by enhanced snowfall, which is partially counteracted by more surface melt and runoff along the <span class="hlt">ice</span> sheet’s edges. This intensifying hydrological cycle is predominantly driven by atmospheric warming, which increases (1) the moisture-carrying capacity of the atmosphere, (2) oceanic source region evaporation, and (3) summer AIS cloud liquid water content.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20150021521&hterms=sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsea','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20150021521&hterms=sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsea"><span>An Assessment of Southern Ocean Water <span class="hlt">Masses</span> and Sea <span class="hlt">Ice</span> During 1988-2007 in a Suite of Interannual CORE-II Simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Downes, Stephanie M.; Farneti, Riccardo; Uotila, Petteri; Griffies, Stephen M.; Marsland, Simon J.; Bailey, David; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20150021521'); toggleEditAbsImage('author_20150021521_show'); toggleEditAbsImage('author_20150021521_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20150021521_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20150021521_hide"></p> <p>2015-01-01</p> <p>We characterise the representation of the Southern Ocean water <span class="hlt">mass</span> structure and sea <span class="hlt">ice</span> within a suite of 15 global ocean-<span class="hlt">ice</span> models run with the Coordinated Ocean-<span class="hlt">ice</span> Reference Experiment Phase II (CORE-II) protocol. The main focus is the representation of the present (1988-2007) mode and intermediate waters, thus framing an analysis of winter and summer mixed layer depths; temperature, salinity, and potential vorticity structure; and temporal variability of sea <span class="hlt">ice</span> distributions. We also consider the interannual variability over the same 20 year period. Comparisons are made between models as well as to observation-based analyses where available. The CORE-II models exhibit several biases relative to Southern Ocean observations, including an underestimation of the model mean mixed layer depths of mode and intermediate water <span class="hlt">masses</span> in March (associated with greater ocean surface heat gain), and an overestimation in September (associated with greater high latitude ocean heat loss and a more northward winter sea-<span class="hlt">ice</span> extent). In addition, the models have cold and fresh/warm and salty water column biases centred near 50 deg S. Over the 1988-2007 period, the CORE-II models consistently simulate spatially variable trends in sea-<span class="hlt">ice</span> concentration, surface freshwater fluxes, mixed layer depths, and 200-700 m ocean heat content. In particular, sea-<span class="hlt">ice</span> coverage around most of the Antarctic continental shelf is reduced, leading to a cooling and freshening of the near surface waters. The shoaling of the mixed layer is associated with increased surface buoyancy gain, except in the Pacific where sea <span class="hlt">ice</span> is also influential. The models are in disagreement, despite the common CORE-II atmospheric state, in their spatial pattern of the 20-year trends in the mixed layer depth and sea-<span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800053750&hterms=methane+composition&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmethane%2Bcomposition','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800053750&hterms=methane+composition&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmethane%2Bcomposition"><span><span class="hlt">Mass</span>-radius relationships and constraints on the composition of Pluto</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lupo, M. J.; Lewis, J. S.</p> <p>1980-01-01</p> <p>With the new upper limit of Pluto's <span class="hlt">mass</span>, an upper limit for Pluto's <span class="hlt">density</span> of 1.74 g/cu cm has been found. Assuming Pluto to be 100% methane, available methane <span class="hlt">density</span> data can be used to set a lower limit of 0.53 g/cu cm on Pluto's <span class="hlt">density</span>, thus placing an absolute upper limit of 1909 km on the radius and a lower limit of 0.32 on the albedo. The results of 280 computer models covering a wide range of composition ratios of rock, water <span class="hlt">ice</span>, and methane <span class="hlt">ice</span> are reported. Limits are placed on Pluto's silicate content, and a simple spacecraft method for determining Pluto's water content from its <span class="hlt">density</span> and moment of inertia is given. The low thermal conductivity and strength of solid methane suggest rapid solid-state convection in Pluto's methane layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11B0906W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11B0906W"><span>Gaussian Process Model for Antarctic Surface <span class="hlt">Mass</span> Balance and <span class="hlt">Ice</span> Core Site Selection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>White, P. A.; Reese, S.; Christensen, W. F.; Rupper, S.</p> <p>2017-12-01</p> <p>Surface <span class="hlt">mass</span> balance (SMB) is an important factor in the estimation of sea level change, and data are collected to estimate models for prediction of SMB on the Antarctic <span class="hlt">ice</span> sheet. Using Favier et al.'s (2013) quality-controlled aggregate data set of SMB field measurements, a fully Bayesian spatial model is posed to estimate Antarctic SMB and propose new field measurement locations. Utilizing Nearest-Neighbor Gaussian process (NNGP) models, SMB is estimated over the Antarctic <span class="hlt">ice</span> sheet. An Antarctic SMB map is rendered using this model and is compared with previous estimates. A prediction uncertainty map is created to identify regions of high SMB uncertainty. The model estimates net SMB to be 2173 Gton yr-1 with 95% credible interval (2021,2331) Gton yr-1. On average, these results suggest lower Antarctic SMB and higher uncertainty than previously purported [Vaughan et al. (1999); Van de Berg et al. (2006); Arthern, Winebrenner and Vaughan (2006); Bromwich et al. (2004); Lenaerts et al. (2012)], even though this model utilizes significantly more observations than previous models. Using the Gaussian process' uncertainty and model parameters, we propose 15 new measurement locations for field study utilizing a maximin space-filling, error-minimizing design; these potential measurements are identied to minimize future estimation uncertainty. Using currently accepted Antarctic <span class="hlt">mass</span> balance estimates and our SMB estimate, we estimate net <span class="hlt">mass</span> loss [Shepherd et al. (2012); Jacob et al. (2012)]. Furthermore, we discuss modeling details for both space-time data and combining field measurement data with output from mathematical models using the NNGP framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4330725','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4330725"><span>Parasitism alters three power laws of scaling in a metazoan community: Taylor’s law, <span class="hlt">density-mass</span> allometry, and variance-<span class="hlt">mass</span> allometry</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lagrue, Clément; Poulin, Robert; Cohen, Joel E.</p> <p>2015-01-01</p> <p>How do the lifestyles (free-living unparasitized, free-living parasitized, and parasitic) of animal species affect major ecological power-law relationships? We investigated this question in metazoan communities in lakes of Otago, New Zealand. In 13,752 samples comprising 1,037,058 organisms, we found that species of different lifestyles differed in taxonomic distribution and body <span class="hlt">mass</span> and were well described by three power laws: a spatial Taylor’s law (the spatial variance in population <span class="hlt">density</span> was a power-law function of the spatial mean population <span class="hlt">density</span>); <span class="hlt">density-mass</span> allometry (the spatial mean population <span class="hlt">density</span> was a power-law function of mean body <span class="hlt">mass</span>); and variance-<span class="hlt">mass</span> allometry (the spatial variance in population <span class="hlt">density</span> was a power-law function of mean body <span class="hlt">mass</span>). To our knowledge, this constitutes the first empirical confirmation of variance-<span class="hlt">mass</span> allometry for any animal community. We found that the parameter values of all three relationships differed for species with different lifestyles in the same communities. Taylor's law and <span class="hlt">density-mass</span> allometry accurately predicted the form and parameter values of variance-<span class="hlt">mass</span> allometry. We conclude that species of different lifestyles in these metazoan communities obeyed the same major ecological power-law relationships but did so with parameters specific to each lifestyle, probably reflecting differences among lifestyles in population dynamics and spatial distribution. PMID:25550506</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AtmEn..99..500D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AtmEn..99..500D"><span>Determination of PM <span class="hlt">mass</span> emissions from an aircraft turbine engine using particle effective <span class="hlt">density</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Durdina, L.; Brem, B. T.; Abegglen, M.; Lobo, P.; Rindlisbacher, T.; Thomson, K. A.; Smallwood, G. J.; Hagen, D. E.; Sierau, B.; Wang, J.</p> <p>2014-12-01</p> <p>Inventories of particulate matter (PM) emissions from civil aviation and air quality models need to be validated using up-to-date measurement data corrected for sampling artifacts. We compared the measured black carbon (BC) <span class="hlt">mass</span> and the total PM <span class="hlt">mass</span> determined from particle size distributions (PSD) and effective <span class="hlt">density</span> for a commercial turbofan engine CFM56-7B26/3. The effective <span class="hlt">density</span> was then used to calculate the PM <span class="hlt">mass</span> losses in the sampling system. The effective <span class="hlt">density</span> was determined using a differential mobility analyzer and a centrifugal particle <span class="hlt">mass</span> analyzer, and increased from engine idle to take-off by up to 60%. The determined <span class="hlt">mass</span>-mobility exponents ranged from 2.37 to 2.64. The mean effective <span class="hlt">density</span> determined by weighting the effective <span class="hlt">density</span> distributions by PM volume was within 10% of the unit <span class="hlt">density</span> (1000 kg/m3) that is widely assumed in aircraft PM studies. We found ratios close to unity between the PM <span class="hlt">mass</span> determined by the integrated PSD method and the real-time BC <span class="hlt">mass</span> measurements. The integrated PSD method achieved higher precision at ultra-low PM concentrations at which current <span class="hlt">mass</span> instruments reach their detection limit. The line loss model predicted ∼60% PM <span class="hlt">mass</span> loss at engine idle, decreasing to ∼27% at high thrust. Replacing the effective <span class="hlt">density</span> distributions with unit <span class="hlt">density</span> lead to comparable estimates that were within 20% and 5% at engine idle and high thrust, respectively. These results could be used for the development of a robust method for sampling loss correction of the future PM emissions database from commercial aircraft engines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JGR....9515959H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JGR....9515959H"><span>One hundred years of Arctic <span class="hlt">ice</span> cover variations as simulated by a one-dimensional, <span class="hlt">ice</span>-ocean model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hakkinen, S.; Mellor, G. L.</p> <p>1990-09-01</p> <p>A one-dimensional <span class="hlt">ice</span>-ocean model consisting of a second moment, turbulent closure, mixed layer model and a three-layer snow-<span class="hlt">ice</span> model has been applied to the simulation of Arctic <span class="hlt">ice</span> <span class="hlt">mass</span> and mixed layer properties. The results for the climatological seasonal cycle are discussed first and include the salt and heat balance in the upper ocean. The coupled model is then applied to the period 1880-1985, using the surface air temperature fluctuations from Hansen et al. (1983) and from Wigley et al. (1981). The analysis of the simulated large variations of the Arctic <span class="hlt">ice</span> <span class="hlt">mass</span> during this period (with similar changes in the mixed layer salinity) shows that the variability in the summer melt determines to a high degree the variability in the average <span class="hlt">ice</span> thickness. The annual oceanic heat flux from the deep ocean and the maximum freezing rate and associated nearly constant minimum surface salinity flux did not vary significantly interannually. This also implies that the oceanic influence on the Arctic <span class="hlt">ice</span> <span class="hlt">mass</span> is minimal for the range of atmospheric variability tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21033806','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21033806"><span>Polarized Raman spectroscopic study of relaxed high <span class="hlt">density</span> amorphous <span class="hlt">ices</span> under pressure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Suzuki, Yoshiharu; Tominaga, Yasunori</p> <p>2010-10-28</p> <p>We have made high <span class="hlt">density</span> amorphous <span class="hlt">ice</span> (HDA) by the pressure-induced amorphization of hexagonal <span class="hlt">ice</span> at 77 K and measured the volume change on isobaric heating in a pressure range between 0.1 and 1.5 GPa. The volume of HDA on heating below ∼0.35 GPa increases, while the volume of HDA on heating above ∼0.35 GPa decreases. The polarized OH-stretching Raman spectra of the relaxed HDAs are compared with that of the unannealed HDA. The relaxed HDAs are prepared at 0.2 GPa at 130 K and 1.5 GPa at 160 K. It is found that the relatively strong totally symmetric OH-stretching vibration mode around 3100 cm(-1) exists in the depolarized reduced Raman spectrum χ(VH)(") of the unannealed HDA and that its intensity rapidly decreases by relaxation. The χ(VH)(") profiles of the relaxed HDA are similar to those of liquid water. These results indicate that the HDA reaches a nearly equilibrium state by annealing and the intrinsic state of HDA relates to a liquid state. The pressure-volume curve of the relaxed HDA at 140 K seems to be smooth in the pressure range below 1.5 GPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27369155','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27369155"><span>A single-phase elastic hyperbolic metamaterial with anisotropic <span class="hlt">mass</span> <span class="hlt">density</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhu, R; Chen, Y Y; Wang, Y S; Hu, G K; Huang, G L</p> <p>2016-06-01</p> <p>Wave propagation can be manipulated at a deep subwavelength scale through the locally resonant metamaterial that possesses unusual effective material properties. Hyperlens due to metamaterial's anomalous anisotropy can lead to superior-resolution imaging. In this paper, a single-phase elastic metamaterial with strongly anisotropic effective <span class="hlt">mass</span> <span class="hlt">density</span> has been designed. The proposed metamaterial utilizes the independently adjustable locally resonant motions of the subwavelength-scale microstructures along the two principal directions. High anisotropy in the effective <span class="hlt">mass</span> <span class="hlt">densities</span> obtained by the numerical-based effective medium theory can be found and even have opposite signs. For practical applications, shunted piezoelectric elements are introduced into the microstructure to tailor the effective <span class="hlt">mass</span> <span class="hlt">density</span> in a broad frequency range. Finally, to validate the design, an elastic hyperlens made of the single-phase hyperbolic metamaterial is proposed with subwavelength longitudinal wave imaging illustrated numerically. The proposed single-phase hyperbolic metamaterial has many promising applications for high resolution damage imaging in nondestructive evaluation and structural health monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130009418','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130009418"><span>Airborne Tomographic Swath <span class="hlt">Ice</span> Sounding Processing System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Xiaoqing; Rodriquez, Ernesto; Freeman, Anthony; Jezek, Ken</p> <p>2013-01-01</p> <p>Glaciers and <span class="hlt">ice</span> sheets modulate global sea level by storing water deposited as snow on the surface, and discharging water back into the ocean through melting. Their physical state can be characterized in terms of their <span class="hlt">mass</span> balance and dynamics. To estimate the current <span class="hlt">ice</span> <span class="hlt">mass</span> balance, and to predict future changes in the motion of the Greenland and Antarctic <span class="hlt">ice</span> sheets, it is necessary to know the <span class="hlt">ice</span> sheet thickness and the physical conditions of the <span class="hlt">ice</span> sheet surface and bed. This information is required at fine resolution and over extensive portions of the <span class="hlt">ice</span> sheets. A tomographic algorithm has been developed to take raw data collected by a multiple-channel synthetic aperture sounding radar system over a polar <span class="hlt">ice</span> sheet and convert those data into two-dimensional (2D) <span class="hlt">ice</span> thickness measurements. Prior to this work, conventional processing techniques only provided one-dimensional <span class="hlt">ice</span> thickness measurements along profiles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0727D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0727D"><span>Continuous measurements of surface <span class="hlt">mass</span> balance, firn compaction, and meltwater retention in Greenland for altimetry validation.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de la Peña, S.; Howat, I.; Behar, A.; Price, S. F.; Thanga, J.; Crowell, J. M.; Huseas, S.; Tedesco, M.</p> <p>2016-12-01</p> <p>Observations made in recent years by repeated altimetry from CryoSat-2 and NASA's Operation <span class="hlt">Ice</span>Bridge reveal large fluctuations in the firn volume of the Greenland <span class="hlt">Ice</span> Sheet. Although an order of magnitude smaller than <span class="hlt">ice</span> thinning rates observed in some areas at the margins of the <span class="hlt">ice</span> sheet, short-term departures in surface elevation trends occur over most of the accumulation zone of Greenland. Changes in the thickness of the firn column are influenced by variability in surface <span class="hlt">mass</span> balance, firn compaction, and abrupt seasonal densification near the surface caused by refreezing at depth of variable amounts of surface meltwater in the summer. These processes and dynamic thinning cannot be differentiated from each other by altimetry alone. Until recently, nearly all information on <span class="hlt">density</span> and surface <span class="hlt">mass</span> balance changes over the firn layer came from <span class="hlt">ice</span> core and snow pit stratigraphy that provided annual rates with relatively large uncertainties. Here we present direct, continuous measurements of firn <span class="hlt">density</span> and surface <span class="hlt">mass</span> balance along with annual estimates of firn <span class="hlt">ice</span> content used to assess observed elevation change in the percolation zone of western Greenland in relation to firn processes. Since 2012, autonomous in-situ firn compaction sensors have monitored several sites in the catchment area of Jakobshavn Isbrae, and since 2015 surface <span class="hlt">mass</span> balance and surface displacement has been measured continuously using a combination of sensors. In addition to identify the different components in the altimetry signal, The temporal resolution of the data acquired provide a means to monitor short-term changes in the near-surface firn, and identifying individual events causing surface elevation displacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33C1210S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33C1210S"><span>Towards development of an operational snow on sea <span class="hlt">ice</span> product</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, J.; Liston, G. E.; Barrett, A. P.; Tschudi, M. A.; Stewart, S.</p> <p>2017-12-01</p> <p>Sea <span class="hlt">ice</span> has been visibly changing over the past couple of decades; most notably the annual minimum extent which has shown a distinct downward, and recently accelerating, trend. September mean sea <span class="hlt">ice</span> extent was over 7×106 km2 in the 1980's, but has averaged less than 5×106 km2 in the last decade. Should this loss continue, there will be wide-ranging impacts on marine ecosystems, coastal communities, prospects for resource extraction and marine activity, and weather conditions in the Arctic and beyond. While changes in the spatial extent of sea <span class="hlt">ice</span> have been routinely monitored since the 1970s, less is known about how the thickness of the <span class="hlt">ice</span> cover has changed. While estimates of <span class="hlt">ice</span> thickness across the Arctic Ocean have become available over the past 20 years based on data from ERS-1/2, Envisat, ICESat, CryoSat-2 satellites and Operation <span class="hlt">Ice</span>Bridge aircraft campaigns, the variety of these different measurement approaches, sensor technologies and spatial coverage present formidable challenges. Key among these is that measurement techniques do not measure <span class="hlt">ice</span> thickness directly - retrievals also require snow depth and <span class="hlt">density</span>. Towards that end, a sophisticated snow accumulation model is tested in a Lagrangian framework to map daily snow depths across the Arctic sea <span class="hlt">ice</span> cover using atmospheric reanalysis data as input. Accuracy of the snow accumulation is assessed through comparison with Operation <span class="hlt">Ice</span>Bridge data and <span class="hlt">ice</span> <span class="hlt">mass</span> balance buoys (IMBs). Impacts on <span class="hlt">ice</span> thickness retrievals are further discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P54B..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P54B..04C"><span>Radar Detection of Layering in <span class="hlt">Ice</span>: Experiments on a Constructed Layered <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carter, L. M.; Koenig, L.; Courville, Z.; Ghent, R. R.; Koutnik, M. R.</p> <p>2016-12-01</p> <p>The polar caps and glaciers of both Earth and Mars display internal layering that preserves a record of past climate. These layers are apparent both in optical datasets (high resolution images, core samples) and in ground penetrating radar (GPR) data. On Mars, the SHARAD (Shallow Radar) radar on the Mars Reconnaissance Orbiter shows fine layering that changes spatially and with depth across the polar caps. This internal layering has been attributed to changes in fractional dust contamination due to obliquity-induced climate variations, but there are other processes that can lead to internal layers visible in radar data. In particular, terrestrial sounding of <span class="hlt">ice</span> sheets compared with core samples have revealed that <span class="hlt">ice</span> <span class="hlt">density</span> and composition differences account for the majority of the radar reflectors. The large cold rooms and <span class="hlt">ice</span> laboratory facility at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) provide us a unique opportunity to construct experimental <span class="hlt">ice</span> sheets in a controlled setting and measure them with radar. In a CRREL laboratory, we constructed a layered <span class="hlt">ice</span> sheet that is 3-m deep with a various snow and <span class="hlt">ice</span> layers with known dust concentrations (using JSC Mars-1 basaltic simulant) and <span class="hlt">density</span> differences. These <span class="hlt">ice</span> sheets were profiled using a commercial GPR, at frequencies of 200, 400 and 900 MHz, to determine how the radar profile changes due to systematic and known changes in snow and <span class="hlt">ice</span> layers, including layers with sub-wavelength spacing. We will report results from these experiments and implications for interpreting radar-detected layering in <span class="hlt">ice</span> on Earth and Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22384073','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22384073"><span>The association of Antarctic krill Euphausia superba with the under-<span class="hlt">ice</span> habitat.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Flores, Hauke; van Franeker, Jan Andries; Siegel, Volker; Haraldsson, Matilda; Strass, Volker; Meesters, Erik Hubert; Bathmann, Ulrich; Wolff, Willem Jan</p> <p>2012-01-01</p> <p>The association of Antarctic krill Euphausia superba with the under-<span class="hlt">ice</span> habitat was investigated in the Lazarev Sea (Southern Ocean) during austral summer, autumn and winter. Data were obtained using novel Surface and Under <span class="hlt">Ice</span> Trawls (SUIT), which sampled the 0-2 m surface layer both under sea <span class="hlt">ice</span> and in open water. Average surface layer <span class="hlt">densities</span> ranged between 0.8 individuals m(-2) in summer and autumn, and 2.7 individuals m(-2) in winter. In summer, under-<span class="hlt">ice</span> <span class="hlt">densities</span> of Antarctic krill were significantly higher than in open waters. In autumn, the opposite pattern was observed. Under winter sea <span class="hlt">ice</span>, <span class="hlt">densities</span> were often low, but repeatedly far exceeded summer and autumn maxima. Statistical models showed that during summer high <span class="hlt">densities</span> of Antarctic krill in the 0-2 m layer were associated with high <span class="hlt">ice</span> coverage and shallow mixed layer depths, among other factors. In autumn and winter, <span class="hlt">density</span> was related to hydrographical parameters. Average under-<span class="hlt">ice</span> <span class="hlt">densities</span> from the 0-2 m layer were higher than corresponding values from the 0-200 m layer collected with Rectangular Midwater Trawls (RMT) in summer. In winter, under-<span class="hlt">ice</span> <span class="hlt">densities</span> far surpassed maximum 0-200 m <span class="hlt">densities</span> on several occasions. This indicates that the importance of the <span class="hlt">ice</span>-water interface layer may be under-estimated by the pelagic nets and sonars commonly used to estimate the population size of Antarctic krill for management purposes, due to their limited ability to sample this habitat. Our results provide evidence for an almost year-round association of Antarctic krill with the under-<span class="hlt">ice</span> habitat, hundreds of kilometres into the <span class="hlt">ice</span>-covered area of the Lazarev Sea. Local concentrations of postlarval Antarctic krill under winter sea <span class="hlt">ice</span> suggest that sea <span class="hlt">ice</span> biota are important for their winter survival. These findings emphasise the susceptibility of an ecological key species to changing sea <span class="hlt">ice</span> habitats, suggesting potential ramifications on Antarctic ecosystems induced by climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3285626','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3285626"><span>The Association of Antarctic Krill Euphausia superba with the Under-<span class="hlt">Ice</span> Habitat</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Flores, Hauke; van Franeker, Jan Andries; Siegel, Volker; Haraldsson, Matilda; Strass, Volker; Meesters, Erik Hubert; Bathmann, Ulrich; Wolff, Willem Jan</p> <p>2012-01-01</p> <p>The association of Antarctic krill Euphausia superba with the under-<span class="hlt">ice</span> habitat was investigated in the Lazarev Sea (Southern Ocean) during austral summer, autumn and winter. Data were obtained using novel Surface and Under <span class="hlt">Ice</span> Trawls (SUIT), which sampled the 0–2 m surface layer both under sea <span class="hlt">ice</span> and in open water. Average surface layer <span class="hlt">densities</span> ranged between 0.8 individuals m−2 in summer and autumn, and 2.7 individuals m−2 in winter. In summer, under-<span class="hlt">ice</span> <span class="hlt">densities</span> of Antarctic krill were significantly higher than in open waters. In autumn, the opposite pattern was observed. Under winter sea <span class="hlt">ice</span>, <span class="hlt">densities</span> were often low, but repeatedly far exceeded summer and autumn maxima. Statistical models showed that during summer high <span class="hlt">densities</span> of Antarctic krill in the 0–2 m layer were associated with high <span class="hlt">ice</span> coverage and shallow mixed layer depths, among other factors. In autumn and winter, <span class="hlt">density</span> was related to hydrographical parameters. Average under-<span class="hlt">ice</span> <span class="hlt">densities</span> from the 0–2 m layer were higher than corresponding values from the 0–200 m layer collected with Rectangular Midwater Trawls (RMT) in summer. In winter, under-<span class="hlt">ice</span> <span class="hlt">densities</span> far surpassed maximum 0–200 m <span class="hlt">densities</span> on several occasions. This indicates that the importance of the <span class="hlt">ice</span>-water interface layer may be under-estimated by the pelagic nets and sonars commonly used to estimate the population size of Antarctic krill for management purposes, due to their limited ability to sample this habitat. Our results provide evidence for an almost year-round association of Antarctic krill with the under-<span class="hlt">ice</span> habitat, hundreds of kilometres into the <span class="hlt">ice</span>-covered area of the Lazarev Sea. Local concentrations of postlarval Antarctic krill under winter sea <span class="hlt">ice</span> suggest that sea <span class="hlt">ice</span> biota are important for their winter survival. These findings emphasise the susceptibility of an ecological key species to changing sea <span class="hlt">ice</span> habitats, suggesting potential ramifications on Antarctic ecosystems induced by climate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.2773E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.2773E"><span>Combined seismic and radar investigation to define <span class="hlt">ice</span> properties and structure of a cold alpine site</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eisen, O.; Bohleber, P.; Drews, R.; Heilig, A.; Hofstede, C.</p> <p>2009-04-01</p> <p>The cold alpine saddle Colle Gnifetti, Monte Rosa, Swiss-Italian Alps resembles very much polar and subpolar <span class="hlt">ice</span> <span class="hlt">masses</span> in terms of glaciological conditions. It has been the site for several <span class="hlt">ice</span>-core drilling campaigns over more than 20 years to determine paleoclimatological and glaciological conditions. To investigate the feasibility of geophysical methods for improved characterization of <span class="hlt">ice</span> <span class="hlt">masses</span> surrounding borehole and <span class="hlt">ice</span>-core sites, a combined active reflection seismic and ground-penetrating radar pilot study has been carried out in summer 2008. Aims are the characterization of <span class="hlt">density</span>, internal layering, seismic and radar wave speed and attenuation, identification of anisotropic features (like crystal orientation or bubble content and shape). Here we present the overall setup and first results. Seismic and GPR profiles were centered on an existing borehole location covering the full <span class="hlt">ice</span> thickness of 62 m. Active seismics was carried out with 24-channel 3-m spacing recording, using a Seismic Impulse Source System (SISSY) along two profiles parallel and perpendicular to the <span class="hlt">ice</span>-flow direction. The same profiles were complemented with GPR measurements utilizing 250, 500 MHz frequencies. Additionally, circular profiles with 250, 500 and 800 MHz were carried out circumferencing the borehole to detect anisotropic features.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2064S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2064S"><span>Using the glacial geomorphology of palaeo-<span class="hlt">ice</span> streams to understand mechanisms of <span class="hlt">ice</span> sheet collapse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stokes, Chris R.; Margold, Martin; Clark, Chris; Tarasov, Lev</p> <p>2017-04-01</p> <p>Processes which bring about <span class="hlt">ice</span> sheet deglaciation are critical to our understanding of glacial-interglacial cycles and <span class="hlt">ice</span> sheet sensitivity to climate change. The precise mechanisms of deglaciation are also relevant to our understanding of modern-day <span class="hlt">ice</span> sheet stability and concerns over global sea level rise. <span class="hlt">Mass</span> loss from <span class="hlt">ice</span> sheets can be broadly partitioned between melting and a 'dynamic' component whereby rapidly-flowing <span class="hlt">ice</span> streams/outlet glaciers transfer <span class="hlt">ice</span> from the interior to the oceans. Surface and basal melting (e.g. of <span class="hlt">ice</span> shelves) are closely linked to atmospheric and oceanic conditions, but the mechanisms that drive dynamic changes in <span class="hlt">ice</span> stream discharge are more complex, which generates much larger uncertainties about their future contribution to <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss and sea level rise. A major problem is that observations of modern-day <span class="hlt">ice</span> streams typically span just a few decades and, at the <span class="hlt">ice</span>-sheet scale, it is unclear how the entire drainage network of <span class="hlt">ice</span> streams evolves during deglaciation. A key question is whether <span class="hlt">ice</span> streams might increase and sustain rates of <span class="hlt">mass</span> loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. To address this issue, numerous workers have sought to understand <span class="hlt">ice</span> stream dynamics over longer time-scales using their glacial geomorphology in the palaeo-record. Indeed, our understanding of their geomorphology has grown rapidly in the last three decades, from almost complete ignorance to a detailed knowledge of their geomorphological products. Building on this body of work, this paper uses the glacial geomorphology of 117 <span class="hlt">ice</span> streams in the North American Laurentide <span class="hlt">Ice</span> Sheet to reconstruct their activity during its deglaciation ( 22,000 to 7,000 years ago). <span class="hlt">Ice</span> stream activity was characterised by high variability in both time and space, with <span class="hlt">ice</span> streams switching on and off in different locations. During deglaciation, we find that their overall number decreased, they occupied a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1258751-developing-bounding-ice-particle-mass-area-dimension-expressions-use-atmospheric-models-remote-sensing','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1258751-developing-bounding-ice-particle-mass-area-dimension-expressions-use-atmospheric-models-remote-sensing"><span>Developing and bounding <span class="hlt">ice</span> particle <span class="hlt">mass</span>- and area-dimension expressions for use in atmospheric models and remote sensing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Erfani, Ehsan; Mitchell, David L.</p> <p>2016-04-07</p> <p>Here, <span class="hlt">ice</span> particle <span class="hlt">mass</span>- and projected area-dimension ( m- D and A- D) power laws are commonly used in the treatment of <span class="hlt">ice</span> cloud microphysical and optical properties and the remote sensing of <span class="hlt">ice</span> cloud properties. Although there has long been evidence that a single m- D or A- D power law is often not valid over all <span class="hlt">ice</span> particle sizes, few studies have addressed this fact. This study develops self-consistent m- D and A- D expressions that are not power laws but can easily be reduced to power laws for the <span class="hlt">ice</span> particle size (maximum dimension or D) rangemore » of interest, and they are valid over a much larger D range than power laws. This was done by combining ground measurements of individual <span class="hlt">ice</span> particle m and D formed at temperature T < –20 °C during a cloud seeding field campaign with 2-D stereo (2D-S) and cloud particle imager (CPI) probe measurements of D and A, and estimates of m, in synoptic and anvil <span class="hlt">ice</span> clouds at similar temperatures. The resulting m- D and A- D expressions are functions of temperature and cloud type (synoptic vs. anvil), and are in good agreement with m- D power laws developed from recent field studies considering the same temperature range (–60 °C < T < –20 °C).« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007237','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007237"><span>Electron <span class="hlt">Density</span> Dropout Near Enceladus in the Context of Water-Vapor and Water-<span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Johnson, R. E.; Kaiser, M. L.; Wahlund, J.-E.; Waite, J. H., Jr.</p> <p>2009-01-01</p> <p>On 12 March 2008, the Cassini spacecraft made a close encounter with the Saturnian moon Enceladus, passing within 52 km of the moon. The spacecraft trajectory was intentionally-oriented in a southerly direction to create a close alignment with the intense water-dominated plumes emitted from the south polar region. During the passage, the Cassini Radio and Plasma Wave System (RPWS) detected two distinct radio signatures: 1) Impulses associated with small water-<span class="hlt">ice</span> dust grain impacts and 2) an upper hybrid (UH) resonance emission that both intensified and displayed a sharp frequency decrease in the near-vicinity of the moon. The frequency decrease of the UH emission is associated with an unexpectedly sharp decrease in electron <span class="hlt">density</span> from approximately 90 el/cubic cm to below 20 el/cubic cm that occurs on a time scale of a minute near the closest encounter with the moon. In this work, we consider a number of scenarios to explain this sharp electron dropout, but surmise that electron absorption by <span class="hlt">ice</span> grains is the most likely process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008E%26PSL.265..246N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008E%26PSL.265..246N"><span>Conditions for a steady <span class="hlt">ice</span> sheet <span class="hlt">ice</span> shelf junction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nowicki, S. M. J.; Wingham, D. J.</p> <p>2008-01-01</p> <p>This paper investigates the conditions under which a marine <span class="hlt">ice</span> sheet may adopt a steady profile. The <span class="hlt">ice</span> is treated as a linear viscous fluid caused to flow from a rigid base to and over water, treated as a denser but inviscid fluid. The solutions in the region around the point of flotation, or 'transition' zone, are calculated numerically. In-flow and out-flow conditions appropriate to <span class="hlt">ice</span> sheet and <span class="hlt">ice</span> shelf flow are applied at the ends of the transition zone and the rigid base is specified; the flow and steady free surfaces are determined as part of the solutions. The basal stress upstream, and the basal deflection downstream, of the flotation point are examined to determine which of these steady solutions satisfy 'contact' conditions that would prevent (i) the steady downstream basal deflection contacting the downstream base, and (ii) the upstream <span class="hlt">ice</span> commencing to float in the event it was melted at the base. In the case that the upstream bed is allowed to slide, we find only one <span class="hlt">mass</span> flux that satisfies the contact conditions. When no sliding is allowed at the bed, however, we find a range of <span class="hlt">mass</span> fluxes satisfy the contact conditions. The effect of 'backpressure' on the solutions is investigated, and is found to have no affect on the qualitative behaviour of the junctions. To the extent that the numerical, linearly viscous treatment may be applied to the case of <span class="hlt">ice</span> flowing out over the ocean, we conclude that when sliding is present, Weertman's 'instability' hypothesis holds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.9455M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.9455M"><span>Submesoscale Sea <span class="hlt">Ice</span>-Ocean Interactions in Marginal <span class="hlt">Ice</span> Zones</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manucharyan, Georgy E.; Thompson, Andrew F.</p> <p>2017-12-01</p> <p>Signatures of ocean eddies, fronts, and filaments are commonly observed within marginal <span class="hlt">ice</span> zones (MIZs) from satellite images of sea <span class="hlt">ice</span> concentration, and in situ observations via <span class="hlt">ice</span>-tethered profilers or underice gliders. However, localized and intermittent sea <span class="hlt">ice</span> heating and advection by ocean eddies are currently not accounted for in climate models and may contribute to their biases and errors in sea <span class="hlt">ice</span> forecasts. Here, we explore mechanical sea <span class="hlt">ice</span> interactions with underlying submesoscale ocean turbulence. We demonstrate that the release of potential energy stored in meltwater fronts can lead to energetic submesoscale motions along MIZs with spatial scales O(10 km) and Rossby numbers O(1). In low-wind conditions, cyclonic eddies and filaments efficiently trap the sea <span class="hlt">ice</span> and advect it over warmer surface ocean waters where it can effectively melt. The horizontal eddy diffusivity of sea <span class="hlt">ice</span> <span class="hlt">mass</span> and heat across the MIZ can reach O(200 m2 s-1). Submesoscale ocean variability also induces large vertical velocities (order 10 m d-1) that can bring relatively warm subsurface waters into the mixed layer. The ocean-sea <span class="hlt">ice</span> heat fluxes are localized over cyclonic eddies and filaments reaching about 100 W m-2. We speculate that these submesoscale-driven intermittent fluxes of heat and sea <span class="hlt">ice</span> can contribute to the seasonal evolution of MIZs. With the continuing global warming and sea <span class="hlt">ice</span> thickness reduction in the Arctic Ocean, submesoscale sea <span class="hlt">ice</span>-ocean processes are expected to become increasingly prominent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22472462-neutron-proton-effective-mass-splitting-terms-symmetry-energy-its-density-slope','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22472462-neutron-proton-effective-mass-splitting-terms-symmetry-energy-its-density-slope"><span>Neutron-proton effective <span class="hlt">mass</span> splitting in terms of symmetry energy and its <span class="hlt">density</span> slope</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chakraborty, S.; Sahoo, B.; Sahoo, S., E-mail: sukadevsahoo@yahoo.com</p> <p>2015-01-15</p> <p>Using a simple <span class="hlt">density</span>-dependent finite-range effective interaction having Yukawa form, the <span class="hlt">density</span> dependence of isoscalar and isovector effective <span class="hlt">masses</span> is studied. The isovector effective <span class="hlt">mass</span> is found to be different for different pairs of like and unlike nucleons. Using HVH theorem, the neutron-proton effective <span class="hlt">mass</span> splitting is represented in terms of symmetry energy and its <span class="hlt">density</span> slope. It is again observed that the neutron-proton effective <span class="hlt">mass</span> splitting has got a positive value when isoscalar effective <span class="hlt">mass</span> is greater than the isovector effective <span class="hlt">mass</span> and has a negative value for the opposite case. Furthermore, the neutron-proton effective <span class="hlt">mass</span> splitting is foundmore » to have a linear dependence on asymmetry β. The second-order symmetry potential has a vital role in the determination of <span class="hlt">density</span> slope of symmetry energy but it does not have any contribution on neutron-proton effective <span class="hlt">mass</span> splitting. The finite-range effective interaction is compared with the SLy2, SKM, f{sub −}, f{sub 0}, and f{sub +} forms of interactions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NPPP..279...47G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NPPP..279...47G"><span>Primary spectrum and composition with <span class="hlt">IceCube/Ice</span>Top</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaisser, Thomas K.; IceCube Collaboration</p> <p>2016-10-01</p> <p><span class="hlt">Ice</span>Cube, with its surface array <span class="hlt">Ice</span>Top, detects three different components of extensive air showers: the total signal at the surface, GeV muons in the periphery of the showers and TeV muons in the deep array of <span class="hlt">Ice</span>Cube. The spectrum is measured with high resolution from the knee to the ankle with <span class="hlt">Ice</span>Top. Composition and spectrum are extracted from events seen in coincidence by the surface array and the deep array of <span class="hlt">Ice</span>Cube. The muon lateral distribution at the surface is obtained from the data and used to provide a measurement of the muon <span class="hlt">density</span> at 600 meters from the shower core up to 30 PeV. Results are compared to measurements from other experiments to obtain an overview of the spectrum and composition over an extended range of energy. Consistency of the surface muon measurements with hadronic interaction models and with measurements at higher energy is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSA51A2400J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSA51A2400J"><span>Contributions of Lower Atmospheric Drivers to the Semiannual Oscillation in Thermospheric Global <span class="hlt">Mass</span> <span class="hlt">Density</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, M., Jr.; Emmert, J. T.; Drob, D. P.; Siskind, D. E.</p> <p>2016-12-01</p> <p>The thermosphere exhibits intra-annual variations (IAV) in globally averaged <span class="hlt">mass</span> <span class="hlt">density</span> that noticeably impact the drag environment of satellites in low Earth orbit. Particularly, the annual and semiannual oscillations (AO and SAO) are collectively the second largest component, after solar variability, of thermospheric global <span class="hlt">mass</span> <span class="hlt">density</span> variations. Several mechanisms have been proposed to explain the oscillations, but they have yet to be reproduced by first-principles modeling simulations. Recent studies have focused on estimating the SAO in eddy diffusion required to explain the thermospheric SAO in <span class="hlt">mass</span> <span class="hlt">density</span>. Less attention has been paid to the effect of lower and middle atmospheric drivers on the lower boundary of the thermosphere. In this study, we utilize the National Center for Atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM), to elucidate how the different lower atmospheric drivers influence IAV, and in particular the SAO of globally-averaged thermospheric <span class="hlt">mass</span> <span class="hlt">density</span>. We performed numerical simulations of a continuous calendar year assuming constant solar forcing, manipulating the lower atmospheric tidal forcing and gravity wave parameterization in order to quantify the SAO in thermospheric <span class="hlt">mass</span> <span class="hlt">density</span> attributable to different lower atmospheric drivers. The prominent initial results are as follows: (1) The "standard" TIME-GCM is capable of simulating the SAO in globally-averaged <span class="hlt">mass</span> <span class="hlt">density</span> at 400 km from first-principles, and its amplitude and phase compare well with empirical models; (2) The simulations suggest that seasonally varying Kzz driven by breaking GWs is not the primary driver of the SAO in upper thermospheric globally averaged <span class="hlt">mass</span> <span class="hlt">density</span>; (3) Preliminary analysis suggests that the SAO in the upper thermospheric <span class="hlt">mass</span> <span class="hlt">density</span> could be a by-product of dynamical wave transport in the mesopause region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140007380','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140007380"><span>Microwave Properties of <span class="hlt">Ice</span>-Phase Hydrometeors for Radar and Radiometers: Sensitivity to Model Assumptions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, Benjamin T.; Petty, Grant W.; Skofronick-Jackson, Gail</p> <p>2012-01-01</p> <p>A simplied framework is presented for assessing the qualitative sensitivities of computed microwave properties, satellite brightness temperatures, and radar reflectivities to assumptions concerning the physical properties of <span class="hlt">ice</span>-phase hydrometeors. Properties considered included the shape parameter of a gamma size distribution andthe melted-equivalent <span class="hlt">mass</span> median diameter D0, the particle <span class="hlt">density</span>, dielectric mixing formula, and the choice of complex index of refraction for <span class="hlt">ice</span>. We examine these properties at selected radiometer frequencies of 18.7, 36.5, 89.0, and 150.0 GHz; and radar frequencies at 2.8, 13.4, 35.6, and 94.0 GHz consistent with existing and planned remote sensing instruments. Passive and active microwave observables of <span class="hlt">ice</span> particles arefound to be extremely sensitive to the melted-equivalent <span class="hlt">mass</span> median diameter D0 ofthe size distribution. Similar large sensitivities are found for variations in the <span class="hlt">ice</span> vol-ume fraction whenever the geometric <span class="hlt">mass</span> median diameter exceeds approximately 1/8th of the wavelength. At 94 GHz the two-way path integrated attenuation is potentially large for dense compact particles. The distribution parameter mu has a relatively weak effect on any observable: less than 1-2 K in brightness temperature and up to 2.7 dB difference in the effective radar reflectivity. Reversal of the roles of <span class="hlt">ice</span> and air in the MaxwellGarnett dielectric mixing formula leads to a signicant change in both microwave brightness temperature (10 K) and radar reflectivity (2 dB). The choice of Warren (1984) or Warren and Brandt (2008) for the complex index of refraction of <span class="hlt">ice</span> can produce a 3%-4% change in the brightness temperature depression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7451H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7451H"><span>Organic components in hair-<span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hofmann, Diana; Steffen, Bernhard; Disko, Ulrich; Wagner, Gerhard; Mätzler, Christian</p> <p>2013-04-01</p> <p>Hair-<span class="hlt">ice</span> is a rather unknown phenomenon. In contrast to generally known frost needles, originating from atmospheric water and expanding e.g. from plant surfaces in all directions, hair <span class="hlt">ice</span> grows from the basis of wet, rotten hardwood. The hair-like, flexible, linear structures may reach up to 10 cm in length without any ramifications. Hair-<span class="hlt">ice</span> appears to be related to the biological activity of a fungus mycelium within the wood. Hair-<span class="hlt">ice</span> can attract winter-active Collemboles (snow flea, Isotoma nivalis). At the onset of hair-<span class="hlt">ice</span> melt a very thin fibre becomes apparent, which carries brownish pearl-like water drops. Therefore, it is supposed that organic substances are inherent, which could possibly act as freezing catalyst as well as recrystallization inhibitor. The aim of this work was the chemical characterization of organic substances contained in hair-<span class="hlt">ice</span>. First analyses of melted hair-<span class="hlt">ice</span> show a total organic carbon (TOC) value of 235 mg/l in contrast to 11 mg/l total nitrogen. Most of inherent nitrogen (70 %) exists thereby as ammonium. Screened by different (<span class="hlt">mass</span> spectrometric) methods, no evidence could be found for the initially expected organic substances like proteins, lipids, small volatile substances or carboxylic acids. By coupling of Ultra Performance Liquid Chromatography with a triple quadrupol <span class="hlt">mass</span> spectrometer (UPLC-MS) a non-resolved chromatogram from a melted hair-<span class="hlt">ice</span> sample was received. Averaged spectra from different regions are similar among themselves with a broad peak spreading over the <span class="hlt">mass</span> range 100-650 Da with favored intense, odd-numbered peaks. Such spectra are similar to dissolved organic matter (DOM), known e.g. from terrestrial and marine waters, soil extracts or aerosols. In the next step, samples were desalted and concentrated by solid phase extraction (SPE) and subsequently analyzed by flow injection analysis (FIA) in a Fourier Transform Ion Cyclotron Resonance <span class="hlt">Mass</span> Spectrometer (FTICR-MS), equipped with an ESI source and a 7 T</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..12210820G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..12210820G"><span>Spring snow conditions on Arctic sea <span class="hlt">ice</span> north of Svalbard, during the Norwegian Young Sea <span class="hlt">ICE</span> (N-<span class="hlt">ICE</span>2015) expedition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallet, Jean-Charles; Merkouriadi, Ioanna; Liston, Glen E.; Polashenski, Chris; Hudson, Stephen; Rösel, Anja; Gerland, Sebastian</p> <p>2017-10-01</p> <p>Snow is crucial over sea <span class="hlt">ice</span> due to its conflicting role in reflecting the incoming solar energy and reducing the heat transfer so that its temporal and spatial variability are important to estimate. During the Norwegian Young Sea <span class="hlt">ICE</span> (N-<span class="hlt">ICE</span>2015) campaign, snow physical properties and variability were examined, and results from April until mid-June 2015 are presented here. Overall, the snow thickness was about 20 cm higher than the climatology for second-year <span class="hlt">ice</span>, with an average of 55 ± 27 cm and 32 ± 20 cm on first-year <span class="hlt">ice</span>. The average <span class="hlt">density</span> was 350-400 kg m-3 in spring, with higher values in June due to melting. Due to flooding in March, larger variability in snow water equivalent was observed. However, the snow structure was quite homogeneous in spring due to warmer weather and lower amount of storms passing over the field camp. The snow was mostly consisted of wind slab, faceted, and depth hoar type crystals with occasional fresh snow. These observations highlight the more dynamic character of evolution of snow properties over sea <span class="hlt">ice</span> compared to previous observations, due to more variable sea <span class="hlt">ice</span> and weather conditions in this area. The snowpack was isothermal as early as 10 June with the first onset of melt clearly identified in early June. Based on our observations, we estimate than snow could be accurately represented by a three to four layers modeling approach, in order to better consider the high variability of snow thickness and <span class="hlt">density</span> together with the rapid metamorphose of the snow in springtime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.3301J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.3301J"><span>The interaction between sea <span class="hlt">ice</span> and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea <span class="hlt">ice</span> cover</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jensen, Mari F.; Nilsson, Johan; Nisancioglu, Kerim H.</p> <p>2016-11-01</p> <p>Changes in the sea <span class="hlt">ice</span> cover of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. In this study, we develop a simple conceptual model to examine how interactions between sea <span class="hlt">ice</span> and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea <span class="hlt">ice</span> covered and salinity stratified Nordic Seas, and consists of a sea <span class="hlt">ice</span> component and a two-layer ocean. The sea <span class="hlt">ice</span> thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea <span class="hlt">ice</span> export. Whether sea <span class="hlt">ice</span> stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the diapycnal flow. In a system where the diapycnal flow increases with <span class="hlt">density</span> differences, the sea <span class="hlt">ice</span> acts as a positive feedback on a freshwater perturbation. If the diapycnal flow decreases with <span class="hlt">density</span> differences, the sea <span class="hlt">ice</span> acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea <span class="hlt">ice</span>. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea <span class="hlt">ice</span>. Generally, the unstable state is reached before the vertical <span class="hlt">density</span> difference disappears, and the temperature of the deep ocean do not need to increase as much as previously thought to provoke abrupt changes in sea <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1614037S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1614037S"><span>Comparing the <span class="hlt">ice</span> nucleation efficiencies of <span class="hlt">ice</span> nucleating substrates to natural mineral dusts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steinke, Isabelle; Funk, Roger; Höhler, Kristina; Haarig, Moritz; Hoffmann, Nadine; Hoose, Corinna; Kiselev, Alexei; Möhler, Ottmar; Leisner, Thomas</p> <p>2014-05-01</p> <p>Mineral dust particles in the atmosphere may act as efficient <span class="hlt">ice</span> nuclei over a wide range of temperature and relative humidity conditions. The <span class="hlt">ice</span> nucleation capability of dust particles mostly depends on the particle surface area and the associated physico-chemical surface properties. It has been observed that the surface-related <span class="hlt">ice</span> nucleation efficiency of different dust particles and mineral species can vary by several orders of magnitude. However, the relation between aerosol surface properties and observed <span class="hlt">ice</span> nucleation efficiency is still not completely understood due to the large variability of chemical compositions and morphological features. In order to gain a better understanding of small scale freezing processes, we investigated the freezing of several hundreds of small droplets (V=0.4 nl) deposited on materials with reasonably well defined surfaces such as crystalline silicon wafers, graphite and freshly cleaved mica sheets under atmospherically relevant conditions. These substrates are intended to serve as simple model structures compared to the surface of natural aerosol particles. To learn more about the impact of particle morphology on <span class="hlt">ice</span> nucleation processes, we also investigated micro-structured silicon wafers with prescribed trenches. The <span class="hlt">ice</span> nucleation efficiencies deduced from these experiments are expressed as <span class="hlt">ice</span> nucleation active surface site <span class="hlt">density</span> values. With this approach, the freezing properties of the above-described substrates could be compared to those of natural mineral dusts such as agricultural soil dusts, volcanic ash and fossil diatoms, which have been investigated in AIDA cloud chamber experiments. All tested <span class="hlt">ice</span> nucleating substrates were consistently less efficient at nucleating <span class="hlt">ice</span> than the natural mineral dusts. Crystalline silicon only had a negligible influence on the freezing of small droplets, leading to freezing near the homogeneous freezing temperature threshold. Applying surface structures to silicon led to a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009DPS....41.1904A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009DPS....41.1904A"><span>Dynamic Tensile Strength of Low Temperature <span class="hlt">Ice</span> and Kuiper Belt Size Distributions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahrens, Thomas J.; Fat'yanov, O. V.; Engelhardt, H.; Fraser, W. C.</p> <p>2009-09-01</p> <p>We model mutual gravitationally driven impact interactions in a nearly gas-free environment of the Kuiper belt (KB) and use low-temperature (< 100 K) <span class="hlt">ice</span> dynamic strength dependent collisional out-come (accretion vs. erosion and fragmentation) models. These lead to theoretically predictable distributions of object number <span class="hlt">density</span>, vs. <span class="hlt">mass</span> distributions. These derived <span class="hlt">mass</span> distributions are comparable to the now rapidly growing KB survey data. Tensional failure of single and polycrystalline <span class="hlt">ice</span> in the temperature range from 263 to 128 K was measured for high strain rate, c.a. 104 s-1, dynamic loading conditions. Experiments, similar to Lange and Ahrens(1991)(LA), were conducted using a gas gun launched Lexan projectile. The liquid nitrogen cooled <span class="hlt">ice</span> target approaching KB-like temperatures was partially confined, rather than using the LA confined geometry. Another set of experiments used a drop tube projectile launcher within the 263 K Caltech <span class="hlt">Ice</span> Laboratory and at 163 K in a liquid nitrogen cooled chamber. New experiments give tensile strengths of 7.6±1.5 MPa at 263 K and 9.1±1.5 MPa at 163 K for unconfined, free of visual initial defects and measurable imperfections <span class="hlt">ice</span> samples. The new strengths are lower than the earlier LA data ( 17 MPa). The major differences arise from <span class="hlt">ice</span> target assembly. LA used polycrystalline <span class="hlt">ice</span> samples confined in annular stainless steel target rings. New measurements were partially confined, in not initially contacting concentric target rings. Later shots used unconfined configurations with <span class="hlt">ice</span> pellets affixed to aluminum foil. Circumferential confinement is known to increase the material damage threshold upon both compression and tensile loading. Previous confinement in LA is the main cause of the above discrepancy. Present tensile strengths are only a few times higher than 0.7 - 3.0 MPa summarized in Petrovic (2003) for quasistatic tension at 10-7 to 10-3 s-1 strain rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C23C..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C23C..03S"><span>Surface water hydrology and the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, L. C.; Yang, K.; Pitcher, L. H.; Overstreet, B. T.; Chu, V. W.; Rennermalm, A. K.; Cooper, M. G.; Gleason, C. J.; Ryan, J.; Hubbard, A.; Tedesco, M.; Behar, A.</p> <p>2016-12-01</p> <p><span class="hlt">Mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet now exceeds 260 Gt/year, raising global sea level by >0.7 mm annually. Approximately two-thirds of this total <span class="hlt">mass</span> loss is now driven by negative <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> balance (SMB), attributed mainly to production and runoff of meltwater from the <span class="hlt">ice</span> sheet surface. This new dominance of runoff as a driver of GrIS total <span class="hlt">mass</span> loss will likely persist owing to anticipated further increases in surface melting, reduced meltwater storage in firn, and the waning importance of dynamical <span class="hlt">mass</span> losses (<span class="hlt">ice</span> calving) as the <span class="hlt">ice</span> sheets retreat from their marine-terminating margins. It also creates the need and opportunity for integrative research pairing traditional surface water hydrology approaches with glaciology. As one example, we present a way to measure supraglacial "runoff" (i.e. specific discharge) at the supraglacial catchment scale ( 101-102 km2), using in situ measurements of supraglacial river discharge and high-resolution satellite/drone mapping of upstream catchment area. This approach, which is standard in terrestrial hydrology but novel for <span class="hlt">ice</span> sheet science, enables independent verification and improvement of modeled SMB runoff estimates used to project sea level rise. Furthermore, because current SMB models do not consider the role of fluvial watershed processes operating on the <span class="hlt">ice</span> surface, inclusion of even a simple surface routing model materially improves simulations of runoff delivered to moulins, the critical pathways for meltwater entry into the <span class="hlt">ice</span> sheet. Incorporating principles of surface water hydrology and fluvial geomorphology and into glaciological models will thus aid estimates of Greenland meltwater runoff to the global ocean as well as connections to subglacial hydrology and <span class="hlt">ice</span> sheet dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11119152','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11119152"><span>Release of cell-free <span class="hlt">ice</span> nuclei from Halomonas elongata expressing the <span class="hlt">ice</span> nucleation gene inaZ of Pseudomonas syringae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tegos, G; Vargas, C; Perysinakis, A; Koukkou, A I; Christogianni, A; Nieto, J J; Ventosa, A; Drainas, C</p> <p>2000-11-01</p> <p>Release of <span class="hlt">ice</span> nuclei in the growth medium of recombinant Halomonas elongata cells expressing the inaZ gene of Pseudomonas syringae was studied in an attempt to produce cell-free active <span class="hlt">ice</span> nuclei for biotechnological applications. Cell-free <span class="hlt">ice</span> nuclei were not retained by cellulose acetate filters of 0.2 microm pore size. Highest activity of cell-free <span class="hlt">ice</span> nuclei was obtained when cells were grown in low salinity (0.5-5% NaCl, w/v). Freezing temperature threshold, estimated to be below -7 degrees C indicating class C nuclei, was not affected by medium salinity. Their <span class="hlt">density</span>, as estimated by Percoll <span class="hlt">density</span> centrifugation, was 1.018 +/- 0.002 gml(-1) and they were found to be free of lipids. <span class="hlt">Ice</span> nuclei are released in the growth medium of recombinant H. elongata cells probably because of inefficient anchoring of the <span class="hlt">ice</span>-nucleation protein aggregates in the outer membrane. The <span class="hlt">ice</span>+ recombinant H. elongata cells could be useful for future use as a source of active cell-free <span class="hlt">ice</span> nucleation protein.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...839...82N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...839...82N"><span>Development of a Full <span class="hlt">Ice</span>-cream Cone Model for Halo Coronal <span class="hlt">Mass</span> Ejections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Na, Hyeonock; Moon, Y.-J.; Lee, Harim</p> <p>2017-04-01</p> <p>It is essential to determine three-dimensional parameters (e.g., radial speed, angular width, and source location) of coronal <span class="hlt">mass</span> ejections (CMEs) for the space weather forecast. In this study, we investigate which cone type represents a halo CME morphology using 29 CMEs (12 Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) halo CMEs and 17 Solar Terrestrial Relations Observatory (STEREO)/Sun-Earth Connection Coronal and Heliospheric Investigation COR2 halo CMEs) from 2010 December to 2011 June. These CMEs are identified as halo CMEs by one spacecraft (SOHO or one of STEREO A and B) and limb ones by the other spacecraft (One of STEREO A and B or SOHO). From cone shape parameters of these CMEs, such as their front curvature, we find that the CME observational structures are much closer to a full <span class="hlt">ice</span>-cream cone type than a shallow <span class="hlt">ice</span>-cream cone type. Thus, we develop a full <span class="hlt">ice</span>-cream cone model based on a new methodology that the full <span class="hlt">ice</span>-cream cone consists of many flat cones with different heights and angular widths to estimate the three-dimensional parameters of the halo CMEs. This model is constructed by carrying out the following steps: (1) construct a cone for a given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (I.e., a triangulation method and a Graduated Cylindrical Shell model).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C21E1165W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C21E1165W"><span>A Detailed Geophysical Investigation of the Grounding of Henry <span class="hlt">Ice</span> Rise, with Implications for Holocene <span class="hlt">Ice</span>-Sheet Extent.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wearing, M.; Kingslake, J.</p> <p>2017-12-01</p> <p>It is generally assumed that since the Last Glacial Maximum the West Antarctic <span class="hlt">Ice</span> Sheet (WAIS) has experienced monotonic retreat of the grounding line (GL). However, recent studies have cast doubt on this assumption, suggesting that the retreat of the WAIS grounding line may have been followed by a significant advance during the Holocene in the Weddell and Ross Sea sectors. Constraining this evolution is important as reconstructions of past <span class="hlt">ice</span>-sheet extent are used to spin-up predictive <span class="hlt">ice</span>-sheet models and correct <span class="hlt">mass</span>-balance observations for glacial isostatic adjustment. Here we examine in detail the formation of the Henry <span class="hlt">Ice</span> Rise (HIR), which <span class="hlt">ice</span>-sheet model simulations suggest played a key role in Holocene <span class="hlt">ice-mass</span> changes in the Weddell Sea sector. Observations from a high-resolution ground-based, <span class="hlt">ice</span>-penetrating radar survey are best explained if the <span class="hlt">ice</span> rise formed when the Ronne <span class="hlt">Ice</span> Shelf grounded on a submarine high, underwent a period of <span class="hlt">ice</span>-rumple flow, before the GL migrated outwards to form the present-day <span class="hlt">ice</span> rise. We constrain the relative chronology of this evolution by comparing the alignment and intersection of isochronal internal layers, relic crevasses, surface features and investigating the dynamic processes leading to their complex structure. We also draw analogies between HIR and the neighbouring Doake <span class="hlt">Ice</span> Rumples. The date of formation is estimated using vertical velocities derived with a phase-sensitive radio-echo sounder (pRES). <span class="hlt">Ice</span>-sheet models suggest that the formation of the HIR and other <span class="hlt">ice</span> rises may have halted and reversed large-scale GL retreat. Hence the small-scale dynamics of these crucial regions could have wide-reaching consequences for future <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> changes and constraining their formation and evolution further would be beneficial. One stringent test of our geophysics-based conclusions would be to drill to the bed of HIR to sample the <span class="hlt">ice</span> for isotopic analysis and the bed for radiocarbon analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0719G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0719G"><span>Surface Melt and Firn <span class="hlt">Density</span> Evolution in the Western Greenland Percolation Zone Over the Past 50 Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Graeter, K.; Osterberg, E. C.; Hawley, R. L.; Thundercloud, Z. R.; Marshall, H. P.; Ferris, D. G.; Lewis, G.</p> <p>2016-12-01</p> <p>Predictions of the Greenland <span class="hlt">Ice</span> Sheet's (GIS) contribution to sea-level rise in a warming climate depend on our ability to model the surface <span class="hlt">mass</span> balance (SMB) processes occurring across the <span class="hlt">ice</span> sheet. These processes are poorly constrained in the percolation zone, the region of the <span class="hlt">ice</span> sheet where surface melt refreezes in the firn, thus preventing that melt from directly contributing to GIS <span class="hlt">mass</span> loss. In this way, the percolation zone serves as a buffer to higher temperatures increasing <span class="hlt">mass</span> loss. However, it is unknown how the percolation zone is evolving in a changing climate and to what extent the region will continue to serve as a buffer to future runoff. We collected seven shallow ( 22-30 m) firn cores from the Western Greenland percolation zone in May-June 2016 as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project. Here we present data on melt layer stratigraphy, <span class="hlt">density</span>, and annual accumulation for each core to determine: (1) the temporal and spatial accumulation and melt refreeze patterns in the percolation zone of W. Greenland over the past 40 - 55 years, and (2) the impacts of changing melt and refreeze patterns on the near-surface <span class="hlt">density</span> profile of the percolation zone. Three of the GreenTrACS firn cores re-occupy firn core sites collected in the 1970's-1990's, allowing us to more accurately quantify the evolution of the percolation zone surface melt and firn <span class="hlt">density</span> during the most recent decades of summertime warming. This work is the basis for broader investigations into how changes in W. Greenland summertime climate are impacting the SMB of the Greenland <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910031726&hterms=greenhouse+effect&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgreenhouse%2Beffect','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910031726&hterms=greenhouse+effect&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgreenhouse%2Beffect"><span>The effect of volume phase changes, <span class="hlt">mass</span> transport, sunlight penetration, and densification on the thermal regime of icy regoliths</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fanale, Fraser P.; Salvail, James R.; Matson, Dennis L.; Brown, Robert H.</p> <p>1990-01-01</p> <p>The present quantitative modeling of convective, condensational, and sublimational effects on porous <span class="hlt">ice</span> crust volumes subjected to solar radiation encompasses the effect of such insolation's penetration of visible bandpass-translucent light, but opaque to the IR bandpass. Quasi-steady-state temperatures, H2O <span class="hlt">mass</span> fluxes, and <span class="hlt">ice</span> <span class="hlt">mass-density</span> change rates are computed as functions of time of day and <span class="hlt">ice</span> depth. When the effects of latent heat and <span class="hlt">mass</span> transport are included in the model, the enhancement of near-surface temperature due to the 'solid-state greenhouse effect' is substantially diminished. When latent heat, <span class="hlt">mass</span> transport, and densification effects are considered, however, a significant solid-state greenhouse effect is shown to be compatible with both morphological evidence for high crust strengths and icy shell decoupling from the lithosphere.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=61546&keyword=high+AND+mountain+AND+ecosystems&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=61546&keyword=high+AND+mountain+AND+ecosystems&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>ION COMPOSITION ELUCIDATION (<span class="hlt">ICE</span>)</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p><br><br>Ion Composition Elucidation (<span class="hlt">ICE</span>) utilizes selected ion recording with a double focusing <span class="hlt">mass</span> spectrometer to simultaneously determine exact <span class="hlt">masses</span> and relative isotopic abundances from <span class="hlt">mass</span> peak profiles. These can be determined more accurately and at higher sensitivity ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C31D..06T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C31D..06T"><span>Submesoscale sea <span class="hlt">ice</span>-ocean interactions in marginal <span class="hlt">ice</span> zones</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, A. F.; Manucharyan, G.</p> <p>2017-12-01</p> <p>Signatures of ocean eddies, fronts and filaments are commonly observed within the marginal <span class="hlt">ice</span> zones (MIZ) from satellite images of sea <span class="hlt">ice</span> concentration, in situ observations via <span class="hlt">ice</span>-tethered profilers or under-<span class="hlt">ice</span> gliders. Localized and intermittent sea <span class="hlt">ice</span> heating and advection by ocean eddies are currently not accounted for in climate models and may contribute to their biases and errors in sea <span class="hlt">ice</span> forecasts. Here, we explore mechanical sea <span class="hlt">ice</span> interactions with underlying submesoscale ocean turbulence via a suite of numerical simulations. We demonstrate that the release of potential energy stored in meltwater fronts can lead to energetic submesoscale motions along MIZs with sizes O(10 km) and Rossby numbers O(1). In low-wind conditions, cyclonic eddies and filaments efficiently trap the sea <span class="hlt">ice</span> and advect it over warmer surface ocean waters where it can effectively melt. The horizontal eddy diffusivity of sea <span class="hlt">ice</span> <span class="hlt">mass</span> and heat across the MIZ can reach O(200 m2 s-1). Submesoscale ocean variability also induces large vertical velocities (order of 10 m day-1) that can bring relatively warm subsurface waters into the mixed layer. The ocean-sea <span class="hlt">ice</span> heat fluxes are localized over cyclonic eddies and filaments reaching about 100 W m-2. We speculate that these submesoscale-driven intermittent fluxes of heat and sea <span class="hlt">ice</span> can potentially contribute to the seasonal evolution of MIZs. With continuing global warming and sea <span class="hlt">ice</span> thickness reduction in the Arctic Ocean, as well as the large expanse of thin sea <span class="hlt">ice</span> in the Southern Ocean, submesoscale sea <span class="hlt">ice</span>-ocean processes are expected to play a significant role in the climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMSH51B2010N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMSH51B2010N"><span>Comparison of Asymmetric and <span class="hlt">Ice</span>-cream Cone Models for Halo Coronal <span class="hlt">Mass</span> Ejections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Na, H.; Moon, Y.</p> <p>2011-12-01</p> <p>Halo coronal <span class="hlt">mass</span> ejections (HCMEs) are major cause of the geomagnetic storms. To minimize the projection effect by coronagraph observation, several cone models have been suggested: an <span class="hlt">ice</span>-cream cone model, an asymmetric cone model etc. These models allow us to determine the three dimensional parameters of HCMEs such as radial speed, angular width, and the angle between sky plane and central axis of the cone. In this study, we compare these parameters obtained from different models using 48 well-observed HCMEs from 2001 to 2002. And we obtain the root mean square error (RMS error) between measured projection speeds and calculated projection speeds for both cone models. As a result, we find that the radial speeds obtained from the models are well correlated with each other (R = 0.86), and the correlation coefficient of angular width is 0.6. The correlation coefficient of the angle between sky plane and central axis of the cone is 0.31, which is much smaller than expected. The reason may be due to the fact that the source locations of the asymmetric cone model are distributed near the center, while those of the <span class="hlt">ice</span>-cream cone model are located in a wide range. The average RMS error of the asymmetric cone model (85.6km/s) is slightly smaller than that of the <span class="hlt">ice</span>-cream cone model (87.8km/s).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.5036N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.5036N"><span>Can we define an asymptotic value for the <span class="hlt">ice</span> active surface site <span class="hlt">density</span> for heterogeneous <span class="hlt">ice</span> nucleation?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank</p> <p>2015-05-01</p> <p>The immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles was investigated. For all particle sizes investigated, a leveling off of the frozen droplet fraction was observed reaching a plateau within the heterogeneous freezing temperature regime (T >- 38°C). The frozen fraction in the plateau region was proportional to the particle surface area. Based on these findings, an asymptotic value for <span class="hlt">ice</span> active surface site <span class="hlt">density</span> ns, which we named ns⋆, could be determined for the investigated feldspar sample. The comparison of these results with those of other studies not only elucidates the general feasibility of determining such an asymptotic value but also shows that the value of ns⋆ strongly depends on the method of the particle surface area determination. However, such an asymptotic value might be an important input parameter for atmospheric modeling applications. At least it shows that care should be taken when ns is extrapolated to lower or higher temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870013913','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870013913"><span>Mechanical and thermal properties of planetologically important <span class="hlt">ices</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Croft, Steven K.</p> <p>1987-01-01</p> <p>Two squences of <span class="hlt">ice</span> composition were proposed for the icy satellites: a dense nebula model and a solar nebula model. Careful modeling of the structure, composition, and thermal history of satellites composed of these various <span class="hlt">ices</span> requires quantitative information on the <span class="hlt">density</span>, compressibility, thermal expansion, heat capacity, and thermal conductivity. Equations of state were fitted to the <span class="hlt">density</span> data of the molecular <span class="hlt">ices</span>. The unusual thermal and mechanical properties of the molecular and binary <span class="hlt">ices</span> suggest a larger range of phenomena than previously anticipated, sufficiently complex perhaps to account for many of the unusual geologic phenomena found on the icy satellites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1255085-reactivation-kamb-ice-stream-tributaries-triggers-century-scale-reorganization-siple-coast-ice-flow-west-antarctica','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1255085-reactivation-kamb-ice-stream-tributaries-triggers-century-scale-reorganization-siple-coast-ice-flow-west-antarctica"><span>Reactivation of Kamb <span class="hlt">Ice</span> Stream tributaries triggers century-scale reorganization of Siple Coast <span class="hlt">ice</span> flow in West Antarctica</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Bougamont, M.; Christoffersen, P.; Price, S. F.; ...</p> <p>2015-10-21</p> <p>Ongoing, centennial-scale flow variability within the Ross <span class="hlt">ice</span> streams of West Antarctica suggests that the present-day positive <span class="hlt">mass</span> balance in this region may reverse in the future. Here we use a three-dimensional <span class="hlt">ice</span> sheet model to simulate <span class="hlt">ice</span> flow in this region over 250 years. The flow responds to changing basal properties, as a subglacial till layer interacts with water transported in an active subglacial hydrological system. We show that a persistent weak bed beneath the tributaries of the dormant Kamb <span class="hlt">Ice</span> Stream is a source of internal <span class="hlt">ice</span> flow instability, which reorganizes all <span class="hlt">ice</span> streams in this region, leadingmore » to a reduced (positive) <span class="hlt">mass</span> balance within decades and a net loss of <span class="hlt">ice</span> within two centuries. This hitherto unaccounted for flow variability could raise sea level by 5 mm this century. Furthermore, better constraints on future sea level change from this region will require improved estimates of geothermal heat flux and subglacial water transport.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24037377','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24037377"><span>Calving fluxes and basal melt rates of Antarctic <span class="hlt">ice</span> shelves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Depoorter, M A; Bamber, J L; Griggs, J A; Lenaerts, J T M; Ligtenberg, S R M; van den Broeke, M R; Moholdt, G</p> <p>2013-10-03</p> <p>Iceberg calving has been assumed to be the dominant cause of <span class="hlt">mass</span> loss for the Antarctic <span class="hlt">ice</span> sheet, with previous estimates of the calving flux exceeding 2,000 gigatonnes per year. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near the calving front. So far, however, no study has reliably quantified the calving flux and the basal <span class="hlt">mass</span> balance (the balance between accretion and ablation at the <span class="hlt">ice</span>-shelf base) for the whole of Antarctica. The distribution of fresh water in the Southern Ocean and its partitioning between the liquid and solid phases is therefore poorly constrained. Here we estimate the <span class="hlt">mass</span> balance components for all <span class="hlt">ice</span> shelves in Antarctica, using satellite measurements of calving flux and grounding-line flux, modelled <span class="hlt">ice</span>-shelf snow accumulation rates and a regional scaling that accounts for unsurveyed areas. We obtain a total calving flux of 1,321 ± 144 gigatonnes per year and a total basal <span class="hlt">mass</span> balance of -1,454 ± 174 gigatonnes per year. This means that about half of the <span class="hlt">ice</span>-sheet surface <span class="hlt">mass</span> gain is lost through oceanic erosion before reaching the <span class="hlt">ice</span> front, and the calving flux is about 34 per cent less than previous estimates derived from iceberg tracking. In addition, the fraction of <span class="hlt">mass</span> loss due to basal processes varies from about 10 to 90 per cent between <span class="hlt">ice</span> shelves. We find a significant positive correlation between basal <span class="hlt">mass</span> loss and surface elevation change for <span class="hlt">ice</span> shelves experiencing surface lowering and enhanced discharge. We suggest that basal <span class="hlt">mass</span> loss is a valuable metric for predicting future <span class="hlt">ice</span>-shelf vulnerability to oceanic forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915674M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915674M"><span>The future of the Devon <span class="hlt">Ice</span> cap: results from climate and <span class="hlt">ice</span> dynamics modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mottram, Ruth; Rodehacke, Christian; Boberg, Fredrik</p> <p>2017-04-01</p> <p>The Devon <span class="hlt">Ice</span> Cap is an example of a relatively well monitored small <span class="hlt">ice</span> cap in the Canadian Arctic. Close to Greenland, it shows a similar surface <span class="hlt">mass</span> balance signal to glaciers in western Greenland. Here we use high resolution (5km) simulations from HIRHAM5 to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic <span class="hlt">ice</span> cap. Observational data from the Devon <span class="hlt">Ice</span> Cap in Arctic Canada is used to evaluate the surface <span class="hlt">mass</span> balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon <span class="hlt">Ice</span> Cap under a warming climate. We find that the Devon <span class="hlt">Ice</span> Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815241S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815241S"><span>Refreezing on the Greenland <span class="hlt">ice</span> sheet: a model comparison</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steger, Christian; Reijmer, Carleen; van den Broeke, Michiel; Ligtenberg, Stefan; Kuipers Munneke, Peter; Noël, Brice</p> <p>2016-04-01</p> <p><span class="hlt">Mass</span> loss of the Greenland <span class="hlt">ice</span> sheet (GrIS) is an important contributor to global sea level rise. Besides calving, surface melt is the dominant source of <span class="hlt">mass</span> loss. However, only part of the surface melt leaves the <span class="hlt">ice</span> sheet as runoff whereas the other part percolates into the snow cover and refreezes. Due to this process, part of the meltwater is (intermediately) stored. Refreezing thus impacts the surface <span class="hlt">mass</span> balance of the <span class="hlt">ice</span> sheet but it also affects the vertical structure of the snow cover due to transport of <span class="hlt">mass</span> and energy. Due to the sparse availability of in situ data and the demand of future projections, it is inevitable to use numerical models to simulate refreezing and related processes. Currently, the magnitude of refrozen <span class="hlt">mass</span> is neither well constrained nor well validated. In this study, we model the snow and firn layer, and compare refreezing on the GrIS as modelled with two different numerical models. Both models are forced with meteorological data from the regional climate model RACMO 2 that has been shown to simulate realistic conditions for Greenland. One model is the UU/IMAU firn densification model (FDM) that can be used both in an on- and offline mode with RACMO 2. The other model is SNOWPACK; a model originally designed to simulate seasonal snow cover in alpine conditions. In contrast to FDM, SNOWPACK accounts for snow metamorphism and microstructure and contains a more physically based snow densification scheme. A first comparison of the models indicates that both seem to be able to capture the general spatial and temporal pattern of refreezing. Spatially, refreezing occurs mostly in the ablation zone and decreases in the accumulation zone towards the interior of the <span class="hlt">ice</span> sheet. Below the equilibrium line altitude (ELA) where refreezing occurs in seasonal snow cover on bare <span class="hlt">ice</span>, the storage effect is only intermediate. Temporal patterns on a seasonal range indicate two peaks in refreezing; one at the beginning of the melt season where</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16782607','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16782607"><span><span class="hlt">Ice</span>-sheet contributions to future sea-level change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gregory, J M; Huybrechts, P</p> <p>2006-07-15</p> <p>Accurate simulation of <span class="hlt">ice</span>-sheet surface <span class="hlt">mass</span> balance requires higher spatial resolution than is afforded by typical atmosphere-ocean general circulation models (AOGCMs), owing, in particular, to the need to resolve the narrow and steep margins where the majority of precipitation and ablation occurs. We have developed a method for calculating <span class="hlt">mass</span>-balance changes by combining <span class="hlt">ice</span>-sheet average time-series from AOGCM projections for future centuries, both with information from high-resolution climate models run for short periods and with a 20km <span class="hlt">ice</span>-sheet <span class="hlt">mass</span>-balance model. Antarctica contributes negatively to sea level on account of increased accumulation, while Greenland contributes positively because ablation increases more rapidly. The uncertainty in the results is about 20% for Antarctica and 35% for Greenland. Changes in <span class="hlt">ice</span>-sheet topography and dynamics are not included, but we discuss their possible effects. For an annual- and area-average warming exceeding 4.5+/-0.9K in Greenland and 3.1+/-0.8K in the global average, the net surface <span class="hlt">mass</span> balance of the Greenland <span class="hlt">ice</span> sheet becomes negative, in which case it is likely that the <span class="hlt">ice</span> sheet would eventually be eliminated, raising global-average sea level by 7m.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA144448','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA144448"><span>Atmospheric <span class="hlt">Icing</span> on Sea Structures,</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1984-04-01</p> <p>structures causes many safety risks and inconve- niences. Ship <span class="hlt">icing</span> has been recognized as a serious problem for a long time and has been discussed in...during an <span class="hlt">icing</span> storm. Also, as will be shown in the theory section, <span class="hlt">ice</span> <span class="hlt">density</span> and type may even vary in constant environmental con- ditions, so...oeiousn aret otn cmalcurglatie for the roplet thabhaecth mdianrvolme dater ofltheug drEt distfriton.ec Ths mehode givese fairlyraccurateyresultsron</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018RvGeo..56..142P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018RvGeo..56..142P"><span>Ocean Tide Influences on the Antarctic and Greenland <span class="hlt">Ice</span> Sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Padman, Laurie; Siegfried, Matthew R.; Fricker, Helen A.</p> <p>2018-03-01</p> <p>Ocean tides are the main source of high-frequency variability in the vertical and horizontal motion of <span class="hlt">ice</span> sheets near their marine margins. Floating <span class="hlt">ice</span> shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of <span class="hlt">ice</span> sheets near their marine margins can also include a tidal component. These tide-induced signals provide insight into the processes by which the oceans can affect <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance and dynamics. In this review, we summarize in situ and satellite-based measurements of the tidal response of <span class="hlt">ice</span> shelves and grounded <span class="hlt">ice</span>, and spatial variability of ocean tide heights and currents around the <span class="hlt">ice</span> sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, <span class="hlt">ice</span> shelf thickness, and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> and extent. We then describe coupled <span class="hlt">ice</span>-ocean models and analytical glacier models that quantify the effect of ocean tides on lower-frequency <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future <span class="hlt">ice</span> sheet <span class="hlt">mass</span> loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, <span class="hlt">ice</span> shelf draft, spatial variability of the drag coefficient at the <span class="hlt">ice</span>-ocean interface, and higher-resolution models with improved representation of tidal energy sinks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41E0713C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41E0713C"><span>Evaluation of a 12-km Satellite-Era Reanalysis of Surface <span class="hlt">Mass</span> Balance for the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cullather, R. I.; Nowicki, S.; Zhao, B.; Max, S.</p> <p>2016-12-01</p> <p>The recent contribution to sea level change from the Greenland <span class="hlt">Ice</span> Sheet is thought to be strongly driven by surface processes including melt and runoff. Global reanalyses are potential means of reconstructing the historical time series of <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> balance (SMB), but lack spatial resolution needed to resolve ablation areas along the periphery of the <span class="hlt">ice</span> sheet. In this work, the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) is used to examine the spatial and temporal variability of surface melt over the Greenland <span class="hlt">Ice</span> Sheet. MERRA-2 is produced for the period 1980 to the present at a grid spacing of ½° latitude by ⅝° longitude, and includes snow hydrology processes including compaction, meltwater percolation and refreezing, runoff, and a prognostic surface albedo. The configuration of the MERRA-2 system allows for the background model - the Goddard Earth Observing System model, version 5 (GEOS-5) - to be carried in phase space through analyzed states via the computation of analysis increments, a capability referred to as "replay". Here, a MERRA-2 replay integration is conducted in which atmospheric forcing fields are interpolated and adjusted to sub- atmospheric grid-scale resolution. These adjustments include lapse-rate effects on temperature, humidity, precipitation, and other atmospheric variables that are known to have a strong elevation dependency over <span class="hlt">ice</span> sheets. The surface coupling is performed such that <span class="hlt">mass</span> and energy are conserved. The atmospheric forcing influences the surface representation, which operates on land surface tiles with an approximate 12-km spacing. This produces a high-resolution, downscaled SMB which is interactively coupled to the reanalysis model. We compare the downscaled SMB product with other reanalyses, regional climate model values, and a second MERRA-2 replay in which the background model has been replaced with a 12-km, non-hydrostatic version of GEOS-5. The assessment</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813180M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813180M"><span>Constraining East Antarctic <span class="hlt">mass</span> trends using a Bayesian inference approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin-Español, Alba; Bamber, Jonathan L.</p> <p>2016-04-01</p> <p> satisfies all the input data, given these constraints. By imposing these conditions, over the period 2003-13 we obtained a <span class="hlt">mass</span> gain due to <span class="hlt">ice</span> dynamics of 103±15 Gt/yr but this was offset by a negative trend in SMB of 47 Gt/yr, resulting in an overall positive trend of 56±15 Gt/yr. Over 2003-08, the <span class="hlt">ice</span> dynamics trend is 96 Gt/yr, offset by a strong negative SMB trend of -81 Gt/yr, with a total <span class="hlt">mass</span> trend of 15±13Gt/yr. Even after relaxing the <span class="hlt">ice</span> dynamics constraint over East Antarctica, we are unable to reproduce the large positive trend obtained in Zwally2015. We conclude that this result is inconsistent with the combined observations, irrespective of any assumption made about the <span class="hlt">density</span> of surface elevation changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930037352&hterms=sonar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsonar','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930037352&hterms=sonar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsonar"><span>Relationship between sea <span class="hlt">ice</span> freeboard and draft in the Arctic Basin, and implications for <span class="hlt">ice</span> thickness monitoring</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wadhams, P.; Tucker, W. B., III; Krabill, W. B.; Swift, R. N.; Comiso, J. C.; Davis, N. R.</p> <p>1992-01-01</p> <p>This study confirms the finding of Comiso et al. (1991) that the probability <span class="hlt">density</span> function (pdf) of the <span class="hlt">ice</span> freeboard in the Arctic Ocean can be converted to a pdf of <span class="hlt">ice</span> draft by applying a simple coordinate factor. The coordinate factor, R, which is the ratio of mean draft to mean freeboard pdf is related to the mean material (<span class="hlt">ice</span> plus snow) <span class="hlt">density</span>, rho(m), and the near-surface water <span class="hlt">density</span> rho(w) by the relationship R = rho(m)/(rho(w) - rho(m)). The measured value of R was applied to each of six 50-km sections north of Greenland of a joint airborne laser and submarine sonar profile obtained along nearly coincident tracks from the Arctic Basin north of Greenland and was found to be consistent over all sections tested, despite differences in the <span class="hlt">ice</span> regime. This indicates that a single value of R might be used for measurements done in this season of the year. The mean value R from all six sections was found to be 7.89.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000074257&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAntarctic%2Bicebergs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000074257&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAntarctic%2Bicebergs"><span>Glacier and <span class="hlt">Ice</span> Shelves Studies Using Satellite SAR Interferometry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, Eric</p> <p>1999-01-01</p> <p>Satellite radar interferometry is a powerful technique to measure the surface velocity and topography of glacier <span class="hlt">ice</span>. On <span class="hlt">ice</span> shelves, a quadruple difference technique separates tidal motion from the steady creep flow deformation of <span class="hlt">ice</span>. The results provide a wealth of information about glacier grounding lines , <span class="hlt">mass</span> fluxes, stability, elastic properties of <span class="hlt">ice</span>, and tidal regime. The grounding line, which is where the glacier detaches from its bed and becomes afloat, is detected with a precision of a few tens of meters. Combining this information with satellite radar altimetry makes it possible to measure glacier discharge into the ocean and state of <span class="hlt">mass</span> balance with greater precision than ever before, and in turn provide a significant revision of past estimates of <span class="hlt">mass</span> balance of the Greenland and Antarctic <span class="hlt">Ice</span> Sheets. Analysis of creep rates on floating <span class="hlt">ice</span> permits an estimation of basal melting at the <span class="hlt">ice</span> shelf underside. The results reveal that the action of ocean water in sub-<span class="hlt">ice</span>-shelf cavities has been largely underestimated by oceanographic models and is the dominant mode of <span class="hlt">mass</span> release to the ocean from an <span class="hlt">ice</span> shelf. Precise mapping of grounding line positions also permits the detection of grounding line migration, which is a fine indicator of glacier change, independent of our knowledge of snow accumulation and <span class="hlt">ice</span> melting. This technique has been successfully used to detect the rapid retreat of Pine Island Glacier, the largest <span class="hlt">ice</span> stream in West Antarctica. Finally, tidal motion of <span class="hlt">ice</span> shelves measured interferometrically provides a modern, synoptic view of the physical processes which govern the formation of tabular icebergs in the Antarctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C51A0254Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C51A0254Y"><span>Modelling the Climate - Greenland <span class="hlt">Ice</span> Sheet Interaction in the Coupled <span class="hlt">Ice</span>-sheet/Climate Model EC-EARTH - PISM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, S.; Madsen, M. S.; Rodehacke, C. B.; Svendsen, S. H.; Adalgeirsdottir, G.</p> <p>2014-12-01</p> <p>Recent observations show that the Greenland <span class="hlt">ice</span> sheet (GrIS) has been losing <span class="hlt">mass</span> with an increasing speed during the past decades. Predicting the GrIS changes and their climate consequences relies on the understanding of the interaction of the GrIS with the climate system on both global and local scales, and requires climate model systems with an explicit and physically consistent <span class="hlt">ice</span> sheet module. A fully coupled global climate model with a dynamical <span class="hlt">ice</span> sheet model for the GrIS has recently been developed. The model system, EC-EARTH - PISM, consists of the EC-EARTH, an atmosphere, ocean and sea <span class="hlt">ice</span> model system, and the Parallel <span class="hlt">Ice</span> Sheet Model (PISM). The coupling of PISM includes a modified surface physical parameterization in EC-EARTH adapted to the land <span class="hlt">ice</span> surface over glaciated regions in Greenland. The PISM <span class="hlt">ice</span> sheet model is forced with the surface <span class="hlt">mass</span> balance (SMB) directly computed inside the EC-EARTH atmospheric module and accounting for the precipitation, the surface evaporation, and the melting of snow and <span class="hlt">ice</span> over land <span class="hlt">ice</span>. PISM returns the simulated basal melt, <span class="hlt">ice</span> discharge and <span class="hlt">ice</span> cover (extent and thickness) as boundary conditions to EC-EARTH. This coupled system is <span class="hlt">mass</span> and energy conserving without being constrained by any anomaly correction or flux adjustment, and hence is suitable for investigation of <span class="hlt">ice</span> sheet - climate feedbacks. Three multi-century experiments for warm climate scenarios under (1) the RCP85 climate forcing, (2) an abrupt 4xCO2 and (3) an idealized 1% per year CO2 increase are performed using the coupled model system. The experiments are compared with their counterparts of the standard CMIP5 simulations (without the interactive <span class="hlt">ice</span> sheet) to evaluate the performance of the coupled system and to quantify the GrIS feedbacks. In particular, the evolution of the Greenland <span class="hlt">ice</span> sheet under the warm climate and its impacts on the climate system are investigated. Freshwater fluxes from the Greenland <span class="hlt">ice</span> sheet melt to the Arctic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..811N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..811N"><span>Modelling the climate and surface <span class="hlt">mass</span> balance of polar <span class="hlt">ice</span> sheets using RACMO2 - Part 1: Greenland (1958-2016)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noël, Brice; van de Berg, Willem Jan; Melchior van Wessem, J.; van Meijgaard, Erik; van As, Dirk; Lenaerts, Jan T. M.; Lhermitte, Stef; Kuipers Munneke, Peter; Smeets, C. J. P. Paul; van Ulft, Lambertus H.; van de Wal, Roderik S. W.; van den Broeke, Michiel R.</p> <p>2018-03-01</p> <p>We evaluate modelled Greenland <span class="hlt">ice</span> sheet (GrIS) near-surface climate, surface energy balance (SEB) and surface <span class="hlt">mass</span> balance (SMB) from the updated regional climate model RACMO2 (1958-2016). The new model version, referred to as RACMO2.3p2, incorporates updated glacier outlines, topography and <span class="hlt">ice</span> albedo fields. Parameters in the cloud scheme governing the conversion of cloud condensate into precipitation have been tuned to correct inland snowfall underestimation: snow properties are modified to reduce drifting snow and melt production in the <span class="hlt">ice</span> sheet percolation zone. The <span class="hlt">ice</span> albedo prescribed in the updated model is lower at the <span class="hlt">ice</span> sheet margins, increasing <span class="hlt">ice</span> melt locally. RACMO2.3p2 shows good agreement compared to in situ meteorological data and point SEB/SMB measurements, and better resolves the spatial patterns and temporal variability of SMB compared with the previous model version, notably in the north-east, south-east and along the K-transect in south-western Greenland. This new model version provides updated, high-resolution gridded fields of the GrIS present-day climate and SMB, and will be used for projections of the GrIS climate and SMB in response to a future climate scenario in a forthcoming study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMNH13C..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMNH13C..03W"><span>Erosion and entrainment of snow and <span class="hlt">ice</span> by pyroclastic <span class="hlt">density</span> currents: some outstanding questions (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walder, J. S.</p> <p>2010-12-01</p> <p> a hot grain flow over snow, although improperly scaled for investigating erosive processes, does demonstrate that snow hydrology and snowpack stability may be critical in the transformation of pyroclastic <span class="hlt">density</span> currents to lahars. When such an experiment is run in a sloping flume, with meltwater able to drain freely at the base of the snow layer, the hot grain flow spreads over the snow surface and then comes to rest--no slurry is produced. In contrast, if meltwater drainage is blocked, the wet snow layer fails at its bed, mobilizes as a slush flow, and mixes with the hot grains to form a slurry. <span class="hlt">Ice</span> layers within a natural snowpack would likewise block meltwater drainage and be conducive to the formation of slush flows. Abrasion and particle impacts—processes that have been studied intensively by engineers concerned with the wear of surfaces in machinery—probably play an important role in the erosion of glacier <span class="hlt">ice</span> by pyroclastic <span class="hlt">density</span> currents. A prime example may be the summit <span class="hlt">ice</span> cap of Nevado del Ruiz, Colombia, which was left grooved by the eruption of 1985 (Thouret, J. Volcanol. Geotherm. Res., v. 41, 1990). Erosion of glacier <span class="hlt">ice</span> is also strongly controlled by the orientation of crevasses, which can “capture” pyroclastic currents. This phenomenon was well displayed at Mount Redoubt, Alaska during the eruptions of 1989-90 and 2009.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663702-development-full-ice-cream-cone-model-halo-coronal-mass-ejections','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663702-development-full-ice-cream-cone-model-halo-coronal-mass-ejections"><span>Development of a Full <span class="hlt">Ice</span>-cream Cone Model for Halo Coronal <span class="hlt">Mass</span> Ejections</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Na, Hyeonock; Moon, Y.-J.; Lee, Harim, E-mail: nho0512@khu.ac.kr, E-mail: moonyj@khu.ac.kr</p> <p></p> <p>It is essential to determine three-dimensional parameters (e.g., radial speed, angular width, and source location) of coronal <span class="hlt">mass</span> ejections (CMEs) for the space weather forecast. In this study, we investigate which cone type represents a halo CME morphology using 29 CMEs (12 Solar and Heliospheric Observatory (SOHO) /Large Angle and Spectrometric Coronagraph (LASCO) halo CMEs and 17 Solar Terrestrial Relations Observatory ( STEREO )/Sun–Earth Connection Coronal and Heliospheric Investigation COR2 halo CMEs) from 2010 December to 2011 June. These CMEs are identified as halo CMEs by one spacecraft ( SOHO or one of STEREO A and B ) and limbmore » ones by the other spacecraft (One of STEREO A and B or SOHO ). From cone shape parameters of these CMEs, such as their front curvature, we find that the CME observational structures are much closer to a full <span class="hlt">ice</span>-cream cone type than a shallow <span class="hlt">ice</span>-cream cone type. Thus, we develop a full <span class="hlt">ice</span>-cream cone model based on a new methodology that the full <span class="hlt">ice</span>-cream cone consists of many flat cones with different heights and angular widths to estimate the three-dimensional parameters of the halo CMEs. This model is constructed by carrying out the following steps: (1) construct a cone for a given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO /LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model).« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10903197','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10903197"><span><span class="hlt">Mass</span> Balance of the Greenland <span class="hlt">Ice</span> Sheet at High Elevations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomas; Akins; Csatho; Fahnestock; Gogineni; Kim; Sonntag</p> <p>2000-07-21</p> <p>Comparison of <span class="hlt">ice</span> discharge from higher elevation areas of the entire Greenland <span class="hlt">Ice</span> Sheet with total snow accumulation gives estimates of <span class="hlt">ice</span> thickening rates over the past few decades. On average, the region has been in balance, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the <span class="hlt">ice</span> sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19879587','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19879587"><span>Ultra-trace determination of Persistent Organic Pollutants in Arctic <span class="hlt">ice</span> using stir bar sorptive extraction and gas chromatography coupled to <span class="hlt">mass</span> spectrometry.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lacorte, S; Quintana, J; Tauler, R; Ventura, F; Tovar-Sánchez, A; Duarte, C M</p> <p>2009-12-04</p> <p>This study presents the optimization and application of an analytical method based on the use of stir bar sorptive extraction (SBSE) gas chromatography coupled to <span class="hlt">mass</span> spectrometry (GC-MS) for the ultra-trace analysis of POPs (Persistent Organic Pollutants) in Arctic <span class="hlt">ice</span>. In a first step, the <span class="hlt">mass</span>-spectrometry conditions were optimized to quantify 48 compounds (polycyclic aromatic hydrocarbons, brominated diphenyl ethers, chlorinated biphenyls, and organochlorinated pesticides) at the low pg/L level. In a second step, the performance of this analytical method was evaluated to determine POPs in Arctic cores collected during an oceanographic campaign. Using a calibration range from 1 to 1800 pg/L and by adjusting acquisition parameters, limits of detection at the 0.1-99 and 102-891 pg/L for organohalogenated compounds and polycyclic aromatic hydrocarbons, respectively, were obtained by extracting 200 mL of unfiltered <span class="hlt">ice</span> water. alpha-hexachlorocyclohexane, DDTs, chlorinated biphenyl congeners 28, 101 and 118 and brominated diphenyl ethers congeners 47 and 99 were detected in <span class="hlt">ice</span> cores at levels between 0.5 to 258 pg/L. We emphasise the advantages and disadvantages of in situ SBSE in comparison with traditional extraction techniques used to analyze POPs in <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JApMe..44..445S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JApMe..44..445S"><span>A Bulk Microphysics Parameterization with Multiple <span class="hlt">Ice</span> Precipitation Categories.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Straka, Jerry M.; Mansell, Edward R.</p> <p>2005-04-01</p> <p>A single-moment bulk microphysics scheme with multiple <span class="hlt">ice</span> precipitation categories is described. It has 2 liquid hydrometeor categories (cloud droplets and rain) and 10 <span class="hlt">ice</span> categories that are characterized by habit, size, and density—two <span class="hlt">ice</span> crystal habits (column and plate), rimed cloud <span class="hlt">ice</span>, snow (<span class="hlt">ice</span> crystal aggregates), three categories of graupel with different <span class="hlt">densities</span> and intercepts, frozen drops, small hail, and large hail. The concept of riming history is implemented for conversions among the graupel and frozen drops categories. The multiple precipitation <span class="hlt">ice</span> categories allow a range of particle <span class="hlt">densities</span> and fall velocities for simulating a variety of convective storms with minimal parameter tuning. The scheme is applied to two cases—an idealized continental multicell storm that demonstrates the <span class="hlt">ice</span> precipitation process, and a small Florida maritime storm in which the warm rain process is important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28753208','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28753208"><span><span class="hlt">Ice</span> nucleation active bacteria in precipitation are genetically diverse and nucleate <span class="hlt">ice</span> by employing different mechanisms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Failor, K C; Schmale, D G; Vinatzer, B A; Monteil, C L</p> <p>2017-12-01</p> <p>A growing body of circumstantial evidence suggests that <span class="hlt">ice</span> nucleation active (<span class="hlt">Ice</span> + ) bacteria contribute to the initiation of precipitation by heterologous freezing of super-cooled water in clouds. However, little is known about the concentration of <span class="hlt">Ice</span> + bacteria in precipitation, their genetic and phenotypic diversity, and their relationship to air <span class="hlt">mass</span> trajectories and precipitation chemistry. In this study, 23 precipitation events were collected over 15 months in Virginia, USA. Air <span class="hlt">mass</span> trajectories and water chemistry were determined and 33 134 isolates were screened for <span class="hlt">ice</span> nucleation activity (INA) at -8 °C. Of 1144 isolates that tested positive during initial screening, 593 had confirmed INA at -8 °C in repeated tests. Concentrations of <span class="hlt">Ice</span> + strains in precipitation were found to range from 0 to 13 219 colony forming units per liter, with a mean of 384±147. Most <span class="hlt">Ice</span> + bacteria were identified as members of known and unknown <span class="hlt">Ice</span> + species in the Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae families, which nucleate <span class="hlt">ice</span> employing the well-characterized membrane-bound INA protein. Two <span class="hlt">Ice</span> + strains, however, were identified as Lysinibacillus, a Gram-positive genus not previously known to include <span class="hlt">Ice</span> + bacteria. INA of the Lysinibacillus strains is due to a nanometer-sized molecule that is heat resistant, lysozyme and proteinase resistant, and secreted. <span class="hlt">Ice</span> + bacteria and the INA mechanisms they employ are thus more diverse than expected. We discuss to what extent the concentration of culturable <span class="hlt">Ice</span> + bacteria in precipitation and the identification of a new heat-resistant biological INA mechanism support a role for <span class="hlt">Ice</span> + bacteria in the initiation of precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913308B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913308B"><span>Longwave radiative effects of Saharan dust during the <span class="hlt">ICE-D</span> campaign</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brooke, Jennifer; Havemann, Stephan; Ryder, Claire; O'Sullivan, Debbie</p> <p>2017-04-01</p> <p>The Havemann-Taylor Fast Radiative Transfer Code (HT-FRTC) is a fast radiative transfer model based on Principal Components. Scattering has been incorporated into HT-FRTC which allows simulations of aerosol as well as clear-sky atmospheres. This work evaluates the scattering scheme in HT-FRTC and investigates dust-affected brightness temperatures using in-situ observations from <span class="hlt">Ice</span> in Clouds Experiment - Dust (<span class="hlt">ICE-D</span>) campaign. The <span class="hlt">ICE-D</span> campaign occurred during August 2015 and was based from Cape Verde. The <span class="hlt">ICE-D</span> campaign is a multidisciplinary project which achieved measurements of in-situ mineral dust properties of the dust advected from the Sahara, and on the aerosol-cloud interactions using the FAAM BAe-146 research aircraft. <span class="hlt">ICE-D</span> encountered a range of low (0.3), intermediate (0.8) and high (1.3) aerosol optical depths, AODs, and therefore provides a range of atmospheric dust loadings in the assessment of dust scattering in HT-FRTC. Spectral radiances in the thermal infrared window region (800 - 1200 cm-1) are sensitive to the presence of mineral dust; mineral dust acts to reduce the upwelling infrared radiation caused by the absorption and re-emission of radiation by the dust layer. ARIES (Airborne Research Interferometer Evaluation System) is a nadir-facing interferometer, measuring infrared radiances between 550 and 3000 cm-1. The ARIES spectral radiances are converted to brightness temperatures by inversion of the Planck function. The mineral dust size distribution is important for radiative transfer applications as it provides a measure of aerosol scattering. The longwave spectral mineral dust optical properties including the <span class="hlt">mass</span> extinction coefficients, single scattering albedos and the asymmetry parameter have been derived from the mean <span class="hlt">ICE-D</span> size distribution. HT-FRTC scattering simulations are initialised with vertical <span class="hlt">mass</span> fractions which can be derived from extinction profiles from the lidar along with the specific extinction coefficient, kext (m2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810050810&hterms=surface+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dsurface%2Bdensity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810050810&hterms=surface+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dsurface%2Bdensity"><span>The dynamics of superclusters - Initial determination of the <span class="hlt">mass</span> <span class="hlt">density</span> of the universe at large scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ford, H. C.; Ciardullo, R.; Harms, R. J.; Bartko, F.</p> <p>1981-01-01</p> <p>The radial velocities of cluster members of two rich, large superclusters have been measured in order to probe the supercluster <span class="hlt">mass</span> <span class="hlt">densities</span>, and simple evolutionary models have been computed to place limits upon the <span class="hlt">mass</span> <span class="hlt">density</span> within each supercluster. These superclusters represent true physical associations of size of about 100 Mpc seen presently at an early stage of evolution. One supercluster is weakly bound, the other probably barely bound, but possibly marginally unbound. Gravity has noticeably slowed the Hubble expansion of both superclusters. Galaxy surface-<span class="hlt">density</span> counts and the <span class="hlt">density</span> enhancement of Abell clusters within each supercluster were used to derive the ratio of <span class="hlt">mass</span> <span class="hlt">densities</span> of the superclusters to the mean field <span class="hlt">mass</span> <span class="hlt">density</span>. The results strongly exclude a closed universe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.718e2017G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.718e2017G"><span>Measurement of the Muon Content of Air Showers with <span class="hlt">Ice</span>Top</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gonzalez, JG; <author pre="for ">IceCube Collaboration</p> <p>2016-05-01</p> <p><span class="hlt">Ice</span>Top, the surface component of the <span class="hlt">Ice</span>Cube detector, has measured the energy spectrum of cosmic ray primaries in the range between 1.6 PeV and 1.3 EeV. <span class="hlt">Ice</span>Top can also be used to measure the average <span class="hlt">density</span> of GeV muons in the shower front at large radial distances (> 300 m) from the shower axis. Wei present the measurement of the muon lateral distribution function for primary cosmic rays with energies between 1.6 PeV and about 0.1 EeV, and compare it to proton and iron simulations. We also discuss how this information can be exploited in the reconstruction of single air shower events. By combining the information on the muon component with that of the electromagnetic component of the air shower, we expect to reduce systematic uncertainties in the inferred <span class="hlt">mass</span> composition of cosmic rays arising from theoretical uncertainties in hadronic interaction models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7865I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7865I"><span>On Land <span class="hlt">Ice</span> <span class="hlt">Mass</span> Change in Southernmost South America, Antarctic Peninsula and Coastal Antarctica consistent with GRACE, GPS and Reconstructed <span class="hlt">Ice</span> History for Past 1000 years.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivins, Erik; Wiese, David; Watkins, Michael; Yuan, Dah-Ning; Landerer, Felix; Simms, Alex; Boening, Carmen</p> <p>2014-05-01</p> <p>The improved spatial coverage provided by high-quality Global Positioning System observing systems on exposed bedrock has allowed these space geodetic experiments to play an increasingly important role in constraining both glacial isostatic adjustment (GIA) processes and viscoelastic responses to present-day glacial <span class="hlt">mass</span> changes (PGMC). Improved constraints on models of <span class="hlt">ice</span> <span class="hlt">mass</span> change in the Southern Hemisphere at present-day, during the Little <span class="hlt">Ice</span> Age, and during the Late Holocene are invaluable for reconciling climate and sea-level variability on a global scale during the present solar radiation forcing and Milankovic orbital configuration. Studies by Jacobs et al. (1992), Whitehouse et al. (2012), King et al. (2012), Boening et al (2012), and others, support the contention that GRACE observations of both GIA and PGMC in the Southern Hemisphere are dominated by the geography and climate of coastal environments. This makes the proper masking of those environments for GRACE-determinations of secular <span class="hlt">mass</span> balance especially sensitive, and downscaling, rescaling, and use of correlation mascon methods a non-trivial part of the analysis. Here we employ two analysis methods to determine the <span class="hlt">mass</span> balances of the Antarctic Peninsula and Patagonia and incorporate GPS observations of ongoing uplift for GIA correction into both. Using data that roughly span 2002-2013, we determine -25 ± 5 Gt/yr for the uncorrected Antarctic Peninsula (AP) and -12 Gt/yr for southern Patagonia and the Cordillera Darwin (PCD). With corrections for GIA these are increased to -34 ± 8 Gt/yr for AP and -22 ± 6 Gt/yr for PCD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41N..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41N..03D"><span>Sensitivity of simulated snow cloud properties to <span class="hlt">mass</span>-diameter parameterizations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duffy, G.; Nesbitt, S. W.; McFarquhar, G. M.</p> <p>2015-12-01</p> <p><span class="hlt">Mass</span> to diameter (m-D) relationships are used in model parameterization schemes to represent <span class="hlt">ice</span> cloud microphysics and in retrievals of bulk cloud properties from remote sensing instruments. One of the most common relationships, used in the current Global Precipitation Measurement retrieval algorithm for example, assigns the <span class="hlt">density</span> of snow as a constant tenth of the <span class="hlt">density</span> of <span class="hlt">ice</span> (0.1g/m^3). This assumption stands in contrast to the results of derived m-D relationships of snow particles, which imply decreasing particle <span class="hlt">densities</span> at larger sizes and result in particle <span class="hlt">masses</span> orders of magnitude below the constant <span class="hlt">density</span> relationship. In this study, forward simulations of bulk cloud properties (e.g., total water content, radar reflectivity and precipitation rate) derived from measured size distributions using several historical m-D relationships are presented. This expands upon previous studies that mainly focused on smaller <span class="hlt">ice</span> particles because of the examination of precipitation-sized particles here. In situ and remote sensing data from the GPM Cold season Experiment (GCPEx) and Canadian CloudSAT/Calypso Validation Program (C3VP), both synoptic snowstorm field experiments in southern Ontario, Canada, are used to evaluate the forward simulations against total water content measured by the Nevzorov and Cloud Spectrometer and Impactor (CSI) probe, radar reflectivity measured by a C band ground based radar and a nadir pointing Ku/Ka dual frequency airborne radar, and precipitation rate measured by a 2D video disdrometer. There are differences between the bulk cloud properties derived using varying m-D relations, with constant <span class="hlt">density</span> assumptions producing results differing substantially from the bulk measured quantities. The variability in bulk cloud properties derived using different m-D relations is compared against the natural variability in those parameters seen in the GCPEx and C3VP field experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018EPJWC.16804010P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018EPJWC.16804010P"><span>Searches for magnetic monopoles with <span class="hlt">Ice</span>Cube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pollmann, Anna</p> <p>2018-01-01</p> <p>Particles that carry a magnetic monopole charge are proposed by various theories which go beyond the Standard Model of particle physics. The expected <span class="hlt">mass</span> of magnetic monopoles varies depending on the theory describing its origin, generally the monopole <span class="hlt">mass</span> far exceeds those which can be created at accelerators. Magnetic monopoles gain kinetic energy in large scale galactic magnetic fields and, depending on their <span class="hlt">mass</span>, can obtain relativistic velocities. <span class="hlt">Ice</span>Cube is a high energy neutrino detector using the clear <span class="hlt">ice</span> at the South Pole as a detection medium. As monopoles pass through this <span class="hlt">ice</span> they produce optical light by a variety of mechanisms. With increasing velocity, they produce light by catalysis of baryon decay, luminescence in the <span class="hlt">ice</span> associated with electronic excitations, indirect and direct Cherenkov light from the monopole track, and Cherenkov light from cascades induced by pair creation and photonuclear reactions. By searching for this light, current best limits for the monopole flux over a broad range of velocities was achieved using the <span class="hlt">Ice</span>Cube detector. A review of these magnetic monopole searches is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22259152','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22259152"><span>Arctic <span class="hlt">ice</span> cover, <span class="hlt">ice</span> thickness and tipping points.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wadhams, Peter</p> <p>2012-02-01</p> <p>We summarize the latest results on the rapid changes that are occurring to Arctic sea <span class="hlt">ice</span> thickness and extent, the reasons for them, and the methods being used to monitor the changing <span class="hlt">ice</span> thickness. Arctic sea <span class="hlt">ice</span> extent had been shrinking at a relatively modest rate of 3-4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer 2007 there was a massive collapse of <span class="hlt">ice</span> extent to a new record minimum of only 4.1 million km(2). Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of <span class="hlt">mass</span> from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques that show the greatest promise on different spatial and temporal scales, and for different purposes. We show results from some recent work from submarines, and speculate that the trends towards retreat and thinning will inevitably lead to an eventual loss of all <span class="hlt">ice</span> in summer, which can be described as a 'tipping point' in that the former situation, of an Arctic covered with mainly multi-year <span class="hlt">ice</span>, cannot be retrieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=Remote+AND+sensing&id=EJ1016786','ERIC'); return false;" href="https://eric.ed.gov/?q=Remote+AND+sensing&id=EJ1016786"><span>Reading the <span class="hlt">Ice</span>: Using Remote Sensing to Analyze Radar Data</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gillette, Brandon; Leinmiller-Renick, Kelsey; Foga, Steve</p> <p>2013-01-01</p> <p>Understanding the behavior of <span class="hlt">ice</span> sheets (thick, continent-size <span class="hlt">ice</span> <span class="hlt">masses</span>) and glaciers (smaller, flowing <span class="hlt">masses</span> of <span class="hlt">ice</span>) is increasingly important as our climate changes, particularly in the Polar Regions. This article describes two lessons, based on the 5E (engage, explore, explain, elaborate, and evaluate) model, that help students practice…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010066068','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010066068"><span>Determining Greenland <span class="hlt">Ice</span> Sheet Accumulation Rates from Radar Remote Sensing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jezek, Kenneth C.</p> <p>2001-01-01</p> <p>An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a <span class="hlt">mass</span> balance investigation of the Greenland <span class="hlt">Ice</span> Sheet. The <span class="hlt">mass</span> balance is calculated by taking the difference between the snow accumulation and the <span class="hlt">ice</span> discharge of the <span class="hlt">ice</span> sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from <span class="hlt">ice</span> core samples taken throughout the <span class="hlt">ice</span> sheet. The sparse data associated with <span class="hlt">ice</span> cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012549','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012549"><span><span class="hlt">Ice</span> sheet topography by satellite altimetry</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brooks, R.L.; Campbell, W.J.; Ramseier, R.O.; Stanley, H.R.; Zwally, H.J.</p> <p>1978-01-01</p> <p>The surface elevation of the southern Greenland <span class="hlt">ice</span> sheet and surface features of the <span class="hlt">ice</span> flow are obtained from the radar altimeter on the GEOS 3 satellite. The achieved accuracy in surface elevation is ???2 m. As changes in surface elevation are indicative of changes in <span class="hlt">ice</span> volume, the <span class="hlt">mass</span> balance of the present <span class="hlt">ice</span> sheets could be determined by repetitive mapping of the surface elevation and the surface could be monitored to detect surging or significant changes in <span class="hlt">ice</span> flow. ?? 1978 Nature Publishing Group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA572179','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA572179"><span><span class="hlt">Mass</span> Balance of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-09-30</p> <p>datasets. Table 1 lists the primary data sources to be used. To determine sources and sinks of MY <span class="hlt">ice</span>, we use a simple model of MY <span class="hlt">ice</span> circulation, which is...shown in Figure 1. In this model , we consider the Beaufort Sea to consist of four zones defined by mean drift of sea <span class="hlt">ice</span> in summer and winter, such...Healy/Louis S. St. Laurant cruises 1 Seasonal <span class="hlt">Ice</span> Zone Observing Network 2 Polar Airborne Measurements and Arctic Regional Climate Model</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29704449','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29704449"><span>Contribution of sea <span class="hlt">ice</span> microbial production to Antarctic benthic communities is driven by sea <span class="hlt">ice</span> dynamics and composition of functional guilds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wing, Stephen R; Leichter, James J; Wing, Lucy C; Stokes, Dale; Genovese, Sal J; McMullin, Rebecca M; Shatova, Olya A</p> <p>2018-04-28</p> <p>Organic matter produced by the sea <span class="hlt">ice</span> microbial community (SIMCo) is an important link between sea <span class="hlt">ice</span> dynamics and secondary production in near-shore food webs of Antarctica. Sea <span class="hlt">ice</span> conditions in McMurdo Sound were quantified from time series of MODIS satellite images for Sept. 1 through Feb. 28 of 2007-2015. A predictable sea <span class="hlt">ice</span> persistence gradient along the length of the Sound and evidence for a distinct change in sea <span class="hlt">ice</span> dynamics in 2011 were observed. We used stable isotope analysis (δ 13 C and δ 15 N) of SIMCo, suspended particulate organic matter (SPOM) and shallow water (10-20 m) macroinvertebrates to reveal patterns in trophic structure of, and incorporation of organic matter from SIMCo into, benthic communities at eight sites distributed along the sea <span class="hlt">ice</span> persistence gradient. <span class="hlt">Mass</span>-balance analysis revealed distinct trophic architecture among communities and large fluxes of SIMCo into the near-shore food web, with the estimates ranging from 2 to 84% of organic matter derived from SIMCo for individual species. Analysis of patterns in <span class="hlt">density</span>, and biomass of macroinvertebrate communities among sites allowed us to model net incorporation of organic matter from SIMCo, in terms of biomass per unit area (g/m 2 ), into benthic communities. Here, organic matter derived from SIMCo supported 39 to 71 per cent of total biomass. Furthermore, for six species, we observed declines in contribution of SIMCo between years with persistent sea <span class="hlt">ice</span> (2008-2009) and years with extensive sea <span class="hlt">ice</span> breakout (2012-2015). Our data demonstrate the vital role of SIMCo in ecosystem function in Antarctica and strong linkages between sea <span class="hlt">ice</span> dynamics and near-shore secondary productivity. These results have important implications for our understanding of how benthic communities will respond to changes in sea <span class="hlt">ice</span> dynamics associated with climate change and highlight the important role of shallow water macroinvertebrate communities as sentinels of change for the Antarctic marine</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..575B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..575B"><span>Investigating <span class="hlt">ice</span> cliff evolution and contribution to glacier <span class="hlt">mass</span>-balance using a physically-based dynamic model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buri, Pascal; Miles, Evan; Ragettli, Silvan; Brun, Fanny; Steiner, Jakob; Pellicciotti, Francesca</p> <p>2016-04-01</p> <p>Supraglacial cliffs are a surface feature typical of debris-covered glaciers, affecting surface evolution, glacier downwasting and <span class="hlt">mass</span> balance by providing a direct <span class="hlt">ice</span>-atmosphere interface. As a result, melt rates can be very high and <span class="hlt">ice</span> cliffs may account for a significant portion of the total glacier <span class="hlt">mass</span> loss. However, their contribution to glacier <span class="hlt">mass</span> balance has rarely been quantified through physically-based models. Most cliff energy balance models are point scale models which calculate energy fluxes at individual cliff locations. Results from the only grid based model to date accurately reflect energy fluxes and cliff melt, but modelled backwasting patterns are in some cases unrealistic, as the distribution of melt rates would lead to progressive shallowing and disappearance of cliffs. Based on a unique multitemporal dataset of cliff topography and backwasting obtained from high-resolution terrestrial and aerial Structure-from-Motion analysis on Lirung Glacier in Nepal, it is apparent that cliffs exhibit a range of behaviours but most do not rapidly disappear. The patterns of evolution cannot be explained satisfactorily by atmospheric melt alone, and are moderated by the presence of supraglacial ponds at the base of cliffs and by cliff reburial with debris. Here, we document the distinct patterns of evolution including disappearance, growth and stability. We then use these observations to improve the grid-based energy balance model, implementing periodic updates of the cliff geometry resulting from modelled melt perpendicular to the <span class="hlt">ice</span> surface. Based on a slope threshold, pixels can be reburied by debris or become debris-free. The effect of ponds are taken into account through enhanced melt rates in horizontal direction on pixels selected based on an algorithm considering distance to the water surface, slope and lake level. We use the dynamic model to first study the evolution of selected cliffs for which accurate, high resolution DEMs are available</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018QSRv..189....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018QSRv..189....1M"><span>Reconciling records of <span class="hlt">ice</span> streaming and <span class="hlt">ice</span> margin retreat to produce a palaeogeographic reconstruction of the deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Margold, Martin; Stokes, Chris R.; Clark, Chris D.</p> <p>2018-06-01</p> <p>This paper reconstructs the deglaciation of the Laurentide <span class="hlt">Ice</span> Sheet (LIS; including the Innuitian <span class="hlt">Ice</span> Sheet) from the Last Glacial Maximum (LGM), with a particular focus on the spatial and temporal variations in <span class="hlt">ice</span> streaming and the associated changes in flow patterns and <span class="hlt">ice</span> divides. We build on a recent inventory of Laurentide <span class="hlt">ice</span> streams and use an existing <span class="hlt">ice</span> margin chronology to produce the first detailed transient reconstruction of the <span class="hlt">ice</span> stream drainage network in the LIS, which we depict in a series of palaeogeographic maps. Results show that the drainage network at the LGM was similar to modern-day Antarctica. The majority of the <span class="hlt">ice</span> streams were marine terminating and topographically-controlled and many of these continued to function late into the deglaciation, until the <span class="hlt">ice</span> sheet lost its marine margin. <span class="hlt">Ice</span> streams with a terrestrial <span class="hlt">ice</span> margin in the west and south were more transient and <span class="hlt">ice</span> flow directions changed with the build-up, peak-phase and collapse of the Cordilleran-Laurentide <span class="hlt">ice</span> saddle. The south-eastern marine margin in Atlantic Canada started to retreat relatively early and some of the <span class="hlt">ice</span> streams in this region switched off at or shortly after the LGM. In contrast, the <span class="hlt">ice</span> streams draining towards the north-western and north-eastern marine margins in the Beaufort Sea and in Baffin Bay appear to have remained stable throughout most of the Late Glacial, and some of them continued to function until after the Younger Dryas (YD). The YD influenced the dynamics of the deglaciation, but there remains uncertainty about the response of the <span class="hlt">ice</span> sheet in several sectors. We tentatively ascribe the switching-on of some major <span class="hlt">ice</span> streams during this period (e.g. M'Clintock Channel <span class="hlt">Ice</span> Stream at the north-west margin), but for other large <span class="hlt">ice</span> streams whose timing partially overlaps with the YD, the drivers are less clear and <span class="hlt">ice</span>-dynamical processes, rather than effects of climate and surface <span class="hlt">mass</span> balance are viewed as more likely drivers. Retreat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApJ...756L..24G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApJ...756L..24G"><span>In-situ Probing of Radiation-induced Processing of Organics in Astrophysical <span class="hlt">Ice</span> Analogs—Novel Laser Desorption Laser Ionization Time-of-flight <span class="hlt">Mass</span> Spectroscopic Studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gudipati, Murthy S.; Yang, Rui</p> <p>2012-09-01</p> <p>Understanding the evolution of organic molecules in <span class="hlt">ice</span> grains in the interstellar medium (ISM) under cosmic rays, stellar radiation, and local electrons and ions is critical to our understanding of the connection between ISM and solar systems. Our study is aimed at reaching this goal of looking directly into radiation-induced processing in these <span class="hlt">ice</span> grains. We developed a two-color laser-desorption laser-ionization time-of-flight <span class="hlt">mass</span> spectroscopic method (2C-MALDI-TOF), similar to matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) <span class="hlt">mass</span> spectroscopy. Results presented here with polycyclic aromatic hydrocarbon (PAH) probe molecules embedded in water-<span class="hlt">ice</span> at 5 K show for the first time that hydrogenation and oxygenation are the primary chemical reactions that occur in astrophysical <span class="hlt">ice</span> analogs when subjected to Lyα radiation. We found that hydrogenation can occur over several unsaturated bonds and the product distribution corresponds to their stabilities. Multiple hydrogenation efficiency is found to be higher at higher temperatures (100 K) compared to 5 K—close to the interstellar <span class="hlt">ice</span> temperatures. Hydroxylation is shown to have similar efficiencies at 5 K or 100 K, indicating that addition of O atoms or OH radicals to pre-ionized PAHs is a barrierless process. These studies—the first glimpses into interstellar <span class="hlt">ice</span> chemistry through analog studies—show that once accreted onto <span class="hlt">ice</span> grains PAHs lose their PAH spectroscopic signatures through radiation chemistry, which could be one of the reason for the lack of PAH detection in interstellar <span class="hlt">ice</span> grains, particularly the outer regions of cold, dense clouds or the upper molecular layers of protoplanetary disks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001APS..MARN17014T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001APS..MARN17014T"><span>The <span class="hlt">mass</span> spectral <span class="hlt">density</span> in quantitative time-of-flight <span class="hlt">mass</span> spectrometry of polymers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tate, Ranjeet S.; Ebeling, Dan; Smith, Lloyd M.</p> <p>2001-03-01</p> <p>Time-of-flight <span class="hlt">mass</span> spectrometry (TOF-MS) is being increasingly used for the study of polymers, for example to obtain the distribution of molecular <span class="hlt">masses</span> for polymer samples. Serious efforts have also been underway to use TOF-MS for DNA sequencing. In TOF-MS the data is obtained in the form of a time-series that represents the distribution in arrival times of ions of various m/z ratios. This time-series data is then converted to a "<span class="hlt">mass</span>-spectrum" via a coordinate transformation from the arrival time (t) to the corresponding <span class="hlt">mass</span>-to-charge ratio (m/z = const. t^2). In this transformation, it is important to keep in mind that spectra are distributions, or <span class="hlt">densities</span> of weight +1, and thus do not transform as functions. To obtain the <span class="hlt">mass</span>-spectral <span class="hlt">density</span>, it is necessary to include a multiplicative factor of √m/z. Common commercial instruments do not take this factor into account. Dropping this factor has no effect on qualitative analysis (detection) or local quantitative measurements, since S/N or signal-to-baseline ratios are unaffected for peaks with small dispersions. However, there are serious consequences for general quantitative analyses. In DNA sequencing applications, loss of signal intensity is in part attributed to multiple charging; however, since the √m/z factor is not taken into account, this conclusion is based on an overestimate (by a factor of √z) of the relative amount of the multiply charged species. In the study of polymers, the normalized dispersion is underestimated by approximately (M_w/Mn -1)/2. In terms of M_w/Mn itself, for example, a M_w/M_n=1.5 calculated without the √m factor corresponds in fact to a M_w/M_n=1.88.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.P34A..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.P34A..05S"><span>Breaking <span class="hlt">Ice</span>: Fracture Processes in Floating <span class="hlt">Ice</span> on Earth and Elsewhere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scambos, T. A.</p> <p>2016-12-01</p> <p>Rapid, intense fracturing events in the <span class="hlt">ice</span> shelves of the Antarctic Peninsula reveal a set of processes that were not fully appreciated prior to the series of <span class="hlt">ice</span> shelf break-ups observed in the late 1990s and early 2000s. A series of studies have uncovered a fascinating array of relationships between climate, ocean, and <span class="hlt">ice</span>: intense widespread hydrofracture; repetitive hydrofracture induced by <span class="hlt">ice</span> plate bending; the ability for sub-surface flooded firn to support hydrofracture; potential triggering by long-period wave action; accelerated fracturing by trapped tsunamic waves; iceberg disintegration, and a remarkable <span class="hlt">ice</span> rebound process from lake drainage that resembles runaway nuclear fission. The events and subsequent studies have shown that rapid regional warming in <span class="hlt">ice</span> shelf areas leads to catastrophic changes in a previously stable <span class="hlt">ice</span> <span class="hlt">mass</span>. More typical fracturing of thick <span class="hlt">ice</span> plates is a natural consequence of <span class="hlt">ice</span> flow in a complex geographic setting, i.e., it is induced by shear and divergence of spreading plate flow around obstacles. While these are not a result of climate or ocean change, weather and ocean processes may impact the exact timing of final separation of an iceberg from a shelf. Taking these terrestrial perspectives to other <span class="hlt">ice</span>-covered ocean worlds, cautiously, provides an observational framework for interpreting features on Europa and Enceladus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7677A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7677A"><span>Melting beneath Greenland outlet glaciers and <span class="hlt">ice</span> streams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, David; Perrette, Mahé; Beckmann, Johanna</p> <p>2015-04-01</p> <p>Basal melting of fast-flowing Greenland outlet glaciers and <span class="hlt">ice</span> streams due to frictional heating at the <span class="hlt">ice</span>-bed interface contributes significantly to total glacier <span class="hlt">mass</span> balance and subglacial meltwater flux, yet modelling this basal melt process in Greenland has received minimal research attention. A one-dimensional dynamic <span class="hlt">ice</span>-flow model is calibrated to the present day longitudinal profiles of 10 major Greenland outlet glaciers and <span class="hlt">ice</span> streams (including the Jakobshavn Isbrae, Petermann Glacier and Helheim Glacier) and is validated against published <span class="hlt">ice</span> flow and surface elevation measurements. Along each longitudinal profile, basal melt is calculated as a function of <span class="hlt">ice</span> flow velocity and basal shear stress. The basal shear stress is dependent on the effective pressure (difference between <span class="hlt">ice</span> overburden pressure and water pressure), basal roughness and a sliding parametrization. Model output indicates that where outlet glaciers and <span class="hlt">ice</span> streams terminate into the ocean with either a small floating <span class="hlt">ice</span> tongue or no floating tongue whatsoever, the proportion of basal melt to total melt (surface, basal and submarine melt) is 5-10% (e.g. Jakobshavn Isbrae; Daugaard-Jensen Glacier). This proportion is, however, negligible where larger <span class="hlt">ice</span> tongues lose <span class="hlt">mass</span> mostly by submarine melt (~1%; e.g. Nioghalvfjerdsfjorden Glacier). Modelled basal melt is highest immediately upvalley of the grounding line, with contributions typically up to 20-40% of the total melt for slippery beds and up to 30-70% for resistant beds. Additionally, modelled grounding line and calving front migration inland for all outlet glaciers and <span class="hlt">ice</span> streams of hundreds of metres to several kilometres occurs. Including basal melt due to frictional heating in outlet glacier and <span class="hlt">ice</span> stream models is important for more accurately modelling <span class="hlt">mass</span> balance and subglacial meltwater flux, and therefore, more accurately modelling outlet glacier and <span class="hlt">ice</span> stream dynamics and responses to future climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1239510-sph-non-newtonian-model-ice-sheet-ice-shelf-dynamics','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1239510-sph-non-newtonian-model-ice-sheet-ice-shelf-dynamics"><span>SPH non-Newtonian Model for <span class="hlt">Ice</span> Sheet and <span class="hlt">Ice</span> Shelf Dynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Tartakovsky, Alexandre M.; Pan, Wenxiao; Monaghan, Joseph J.</p> <p>2012-07-07</p> <p>We propose a new three-dimensional smoothed particle hydrodynamics (SPH) non-Newtonian model to study coupled <span class="hlt">ice</span> sheet and <span class="hlt">ice</span> shelf dynamics. Most existing <span class="hlt">ice</span> sheet numerical models use a grid-based Eulerian approach, and are usually restricted to shallow <span class="hlt">ice</span> sheet and <span class="hlt">ice</span> shelf approximations of the momentum conservation equation. SPH, a fully Lagrangian particle method, solves the full momentum conservation equation. SPH method also allows modeling of free-surface flows, large material deformation, and material fragmentation without employing complex front-tracking schemes, and does not require re-meshing. As a result, SPH codes are highly scalable. Numerical accuracy of the proposed SPH model ismore » first verified by simulating a plane shear flow with a free surface and the propagation of a blob of <span class="hlt">ice</span> along a horizontal surface. Next, the SPH model is used to investigate the grounding line dynamics of <span class="hlt">ice</span> sheet/shelf. The steady position of the grounding line, obtained from our SPH simulations, is in good agreement with laboratory observations for a wide range of bedrock slopes, <span class="hlt">ice</span>-to-fluid <span class="hlt">density</span> ratios, and flux. We examine the effect of non-Newtonian behavior of <span class="hlt">ice</span> on the grounding line dynamics. The non-Newtonian constitutive model is based on Glen's law for a creeping flow of a polycrystalline <span class="hlt">ice</span>. Finally, we investigate the effect of a bedrock geometry on a steady-state position of the grounding line.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=density&pg=7&id=EJ766056','ERIC'); return false;" href="https://eric.ed.gov/?q=density&pg=7&id=EJ766056"><span>Finding the <span class="hlt">Density</span> of Objects without Measuring <span class="hlt">Mass</span> and Volume</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Mumba, Frackson; Tsige, Mesfin</p> <p>2007-01-01</p> <p>A simple method based on the moment of forces and Archimedes' principle is described for finding <span class="hlt">density</span> without measuring the <span class="hlt">mass</span> and volume of an object. The method involves balancing two unknown objects of <span class="hlt">masses</span> M[subscript 1] and M[subscript 2] on each side of a pivot on a metre rule and measuring their corresponding moment arms. The object…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930006213','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930006213"><span>Advancements in the LEWICE <span class="hlt">Ice</span> Accretion Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wright, William B.</p> <p>1993-01-01</p> <p>Recent evidence has shown that the NASA/Lewis <span class="hlt">Ice</span> Accretion Model, LEWICE, does not predict accurate <span class="hlt">ice</span> shapes for certain glaze <span class="hlt">ice</span> conditions. This paper will present the methodology used to make a first attempt at improving the <span class="hlt">ice</span> accretion prediction in these regimes. Importance is given to the correlations for heat transfer coefficient and <span class="hlt">ice</span> <span class="hlt">density</span>, as well as runback flow, selection of the transition point, flow field resolution, and droplet trajectory models. Further improvements and refinement of these modules will be performed once tests in NASA's <span class="hlt">Icing</span> Research Tunnel, scheduled for 1993, are completed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/7061','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/7061"><span>Columbia Glacier stake location, <span class="hlt">mass</span> balance, glacier surface altitude, and <span class="hlt">ice</span> radar data, 1978 measurement year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Mayo, L.R.; Trabant, D.C.; March, Rod; Haeberli, Wilfried</p> <p>1979-01-01</p> <p>A 1 year data-collection program on Columbia Glacier, Alaska has produced a data set consisting of near-surface <span class="hlt">ice</span> kinematics, <span class="hlt">mass</span> balance, and altitude change at 57 points and 34 <span class="hlt">ice</span> radar soundings. These data presented in two tables, are part of the basic data required for glacier dynamic analysis, computer models, and predictions of the number and size of icebergs which Columbia Glacier will calve into shipping lanes of eastern Prince William Sound. A metric, sea-level coordinate system was developed for use in surveying throughout the basin. Its use is explained and monument coordinates listed. A series of seven integrated programs for calculators were used in both the field and office to reduce the surveying data. These programs are thoroughly documented and explained in the report. (Kosco-USGS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29852466','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29852466"><span>Lung <span class="hlt">mass</span> <span class="hlt">density</span> analysis using deep neural network and lung ultrasound surface wave elastography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Boran; Zhang, Xiaoming</p> <p>2018-05-23</p> <p>Lung <span class="hlt">mass</span> <span class="hlt">density</span> is directly associated with lung pathology. Computed Tomography (CT) evaluates lung pathology using the Hounsfield unit (HU) but not lung <span class="hlt">density</span> directly. We have developed a lung ultrasound surface wave elastography (LUSWE) technique to measure the surface wave speed of superficial lung tissue. The objective of this study was to develop a method for analyzing lung <span class="hlt">mass</span> <span class="hlt">density</span> of superficial lung tissue using a deep neural network (DNN) and synthetic data of wave speed measurements with LUSWE. The synthetic training dataset of surface wave speed, excitation frequency, lung <span class="hlt">mass</span> <span class="hlt">density</span>, and viscoelasticity from LUSWE (788,000 in total) was used to train the DNN model. The DNN was composed of 3 hidden layers of 1024 neurons for each layer and trained for 10 epochs with a batch size of 4096 and a learning rate of 0.001 with three types of optimizers. The test dataset (4000) of wave speeds at three excitation frequencies (100, 150, and 200 Hz) and shear elasticity of superficial lung tissue was used to predict the lung <span class="hlt">density</span> and evaluate its accuracy compared with predefined lung <span class="hlt">mass</span> <span class="hlt">densities</span>. This technique was then validated on a sponge phantom experiment. The obtained results showed that predictions matched well with test dataset (validation accuracy is 0.992) and experimental data in the sponge phantom experiment. This method may be useful to analyze lung <span class="hlt">mass</span> <span class="hlt">density</span> by using the DNN model together with the surface wave speed and lung stiffness measurements. Copyright © 2018 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5867S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5867S"><span>Changes in <span class="hlt">ice</span> dynamics along the northern Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seehaus, Thorsten; Marinsek, Sebastian; Cook, Alison; Van Wessem, Jan-Melchior; Braun, Matthias</p> <p>2017-04-01</p> <p>The climatic conditions along the Antarctic Peninsula have undergone considerable changes during the last 50 years. A period of pronounced air temperature rise, increasing ocean temperatures as well as changes in the precipitation pattern have been reported by various authors. Consequently, the glacial systems showed changes including widespread retreat, surface lowering as well as variations in flow speeds. During the last decades numerous <span class="hlt">ice</span> shelves along the Antarctic Peninsula retreated, started to break-up or disintegrated completely. The loss of the buttressing effect caused tributary glaciers to accelerate with increasing <span class="hlt">ice</span> discharge along the Antarctic Peninsula. Quantification of the <span class="hlt">mass</span> changes is still subject to considerable errors although numbers derived from the different methods are converging. The aim is to study the reaction of glaciers at the northern Antarctic Peninsula to the changing climatic conditions and the readjustments of tributary glaciers to <span class="hlt">ice</span> shelf disintegration, as well as to better quantify the <span class="hlt">ice</span> <span class="hlt">mass</span> loss and its temporal changes. We analysed time series of various satellite sensors (ERS-1/2 SAR, ENVISAT ASAR, RADARSAT-1, ALOS PALSAR, TerraSAR-X/TanDEM-X, ASTER, Landsat) to detect changes in <span class="hlt">ice</span> dynamics of 74 glacier basins along the northern Antarctic Peninsula (<65°). Intensity feature tracking techniques were applied on data stacks from different SAR satellites over the last 20 years to infer temporal trends in glacier surface velocities. In combination with <span class="hlt">ice</span> thickness reconstructions and modeled climatic <span class="hlt">mass</span> balance fields regional imbalances were calculated. Variations in <span class="hlt">ice</span> front position were mapped based on optical and SAR satellite data sets. Along the west coast of the northern Antarctic Peninsula an increase in flow speeds by 40% between 1992 and 2014 was observed, whereas glaciers on the east side (north of former Prince-Gustav <span class="hlt">Ice</span> Shelf) showed a strong deceleration. Nearly all former <span class="hlt">ice</span> shelf</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830062257&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmarginal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830062257&hterms=marginal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmarginal"><span>Sensitivity studies with a coupled <span class="hlt">ice</span>-ocean model of the marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roed, L. P.</p> <p>1983-01-01</p> <p>An analytical coupled <span class="hlt">ice</span>-ocean model is considered which is forced by a specified wind stress acting on the open ocean as well as the <span class="hlt">ice</span>. The analysis supports the conjecture that the upwelling dynamics at <span class="hlt">ice</span> edges can be understood by means of a simple analytical model. In similarity with coastal problems it is shown that the <span class="hlt">ice</span> edge upwelling is determined by the net <span class="hlt">mass</span> flux at the boundaries of the considered region. The model is used to study the sensitivity of the upwelling dynamics in the marginal <span class="hlt">ice</span> zone to variation in the controlling parameters. These parameters consist of combinations of the drag coefficients used in the parameterization of the stresses on the three interfaces atmosphere-<span class="hlt">ice</span>, atmosphere-ocean, and <span class="hlt">ice</span>-ocean. The response is shown to be sensitive to variations in these parameters in that one set of parameters may give upwelling while a slightly different set of parameters may give downwelling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19884496','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19884496"><span>The future of <span class="hlt">ice</span> sheets and sea <span class="hlt">ice</span>: between reversible retreat and unstoppable loss.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Notz, Dirk</p> <p>2009-12-08</p> <p>We discuss the existence of cryospheric "tipping points" in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea <span class="hlt">ice</span> and the retreat of <span class="hlt">ice</span> sheets: Once these <span class="hlt">ice</span> <span class="hlt">masses</span> have shrunk below an anticipated critical extent, the <span class="hlt">ice</span>-albedo feedback might lead to the irreversible and unstoppable loss of the remaining <span class="hlt">ice</span>. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea <span class="hlt">ice</span>. Hence, in a cooler climate, sea <span class="hlt">ice</span> could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea <span class="hlt">ice</span> might largely be a consequence of a slow shift in <span class="hlt">ice</span>-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-<span class="hlt">ice</span> extent. This variability will render seasonal forecasts of the Arctic summer sea-<span class="hlt">ice</span> extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea <span class="hlt">ice</span>, a tipping point is more likely to exist for the loss of the Greenland <span class="hlt">ice</span> sheet and the West Antarctic <span class="hlt">ice</span> sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.C11A0094S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.C11A0094S"><span>Estimation of Greenland's <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> Balance Using ICESat and GRACE Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slobbe, D.; Ditmar, P.; Lindenbergh, R.</p> <p>2007-12-01</p> <p>Data of the GRACE gravity mission and the ICESat laser altimetry mission are used to create two independent estimates of Greenland's <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance over the full measurement period. For ICESat data, a processing strategy is developed using the elevation differences of geometrically overlapping footprints of both crossing and repeated tracks. The dataset is cleaned using quality flags defined by the GLAS science team. The cleaned dataset reveals some strong, spatially correlated signals that are shown to be related to physical phenomena. Different processing strategies are used to convert the observed temporal height differences to <span class="hlt">mass</span> changes for 6 different drainage systems, further divided into a region above and below 2000 meter elevation. The results are compared with other altimetry based <span class="hlt">mass</span> balance estimates. In general, the obtained results confirm trends discovered by others, but we also show that the choice of processing strategy strongly influences our results, especially for the areas below 2000 meter. Furthermore, GRACE based monthly variations of the Earth's gravity field as processed by CNES, CSR, GFZ and DEOS are used to estimate the <span class="hlt">mass</span> balance change for North and South Greenland. It is shown that our results are comparable with recently published GRACE estimates (mascon solutions). On the other hand, the estimates based on GRACE data are only partly confirmed by the ICESat estimates. Possible explanations for the obvious differences will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4086A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4086A"><span>Variable Basal Melt Rates of Antarctic Peninsula <span class="hlt">Ice</span> Shelves, 1994-2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adusumilli, Susheel; Fricker, Helen Amanda; Siegfried, Matthew R.; Padman, Laurie; Paolo, Fernando S.; Ligtenberg, Stefan R. M.</p> <p>2018-05-01</p> <p>We have constructed 23-year (1994-2016) time series of Antarctic Peninsula (AP) <span class="hlt">ice</span>-shelf height change using data from four satellite radar altimeters (ERS-1, ERS-2, Envisat, and CryoSat-2). Combining these time series with output from atmospheric and firn models, we partitioned the total height-change signal into contributions from varying surface <span class="hlt">mass</span> balance, firn state, <span class="hlt">ice</span> dynamics, and basal <span class="hlt">mass</span> balance. On the Bellingshausen coast of the AP, <span class="hlt">ice</span> shelves lost 84 ± 34 Gt a-1 to basal melting, compared to contributions of 50 ± 7 Gt a-1 from surface <span class="hlt">mass</span> balance and <span class="hlt">ice</span> dynamics. Net basal melting on the Weddell coast was 51 ± 71 Gt a-1. Recent changes in <span class="hlt">ice</span>-shelf height include increases over major AP <span class="hlt">ice</span> shelves driven by changes in firn state. Basal melt rates near Bawden <span class="hlt">Ice</span> Rise, a major pinning point of Larsen C <span class="hlt">Ice</span> Shelf, showed large increases, potentially leading to substantial loss of buttressing if sustained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050240943&hterms=surface+density&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsurface%2Bdensity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050240943&hterms=surface+density&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsurface%2Bdensity"><span>The Minimum-<span class="hlt">Mass</span> Surface <span class="hlt">Density</span> of the Solar Nebula using the Disk Evolution Equation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, Sanford S.</p> <p>2005-01-01</p> <p>The Hayashi minimum-<span class="hlt">mass</span> power law representation of the pre-solar nebula (Hayashi 1981, Prog. Theo. Phys.70,35) is revisited using analytic solutions of the disk evolution equation. A new cumulative-planetary-<span class="hlt">mass</span>-model (an integrated form of the surface <span class="hlt">density</span>) is shown to predict a smoother surface <span class="hlt">density</span> compared with methods based on direct estimates of surface <span class="hlt">density</span> from planetary data. First, a best-fit transcendental function is applied directly to the cumulative planetary <span class="hlt">mass</span> data with the surface <span class="hlt">density</span> obtained by direct differentiation. Next a solution to the time-dependent disk evolution equation is parametrically adapted to the planetary data. The latter model indicates a decay rate of r -1/2 in the inner disk followed by a rapid decay which results in a sharper outer boundary than predicted by the minimum <span class="hlt">mass</span> model. The model is shown to be a good approximation to the finite-size early Solar Nebula and by extension to extra solar protoplanetary disks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..187K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..187K"><span>Last Glacial-Interglacial Transition <span class="hlt">ice</span> dynamics in the Wicklow Mountains, Ireland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knight, Lauren; Boston, Clare; Lovell, Harold; Pepin, Nick</p> <p>2017-04-01</p> <p>Understanding of the extent and dynamics of former <span class="hlt">ice</span> <span class="hlt">masses</span> in the Wicklow Mountains, Ireland, during the Last Glacial-Interglacial Transition (LGIT; 15-10 ka BP) is currently unresolved. Whilst it is acknowledged that the region hosted a local <span class="hlt">ice</span> cap within the larger British-Irish <span class="hlt">Ice</span> Sheet at the Last Glacial Maximum (LGM; 27 ka BP), there has been little consideration of <span class="hlt">ice</span> cap disintegration to a topographically constrained <span class="hlt">ice</span> <span class="hlt">mass</span> during the LGIT. This research has produced the first regional glacial geomorphological map, through remote sensing (aerial photograph and digital terrain model interrogation) and field mapping. This has allowed both the style and extent of mountain glaciation and <span class="hlt">ice</span> recession dynamics during the LGIT to be established. This geomorphological mapping has highlighted that evidence for local glaciation in the Wicklow Mountains is more extensive than previously recognised, and that small icefields and associated outlet valley glaciers existed during the LGIT following disintegration of the Wicklow <span class="hlt">Ice</span> Cap. A relative chronology based on morphostratigraphic principles is developed, which indicates complex patterns of <span class="hlt">ice</span> <span class="hlt">mass</span> oscillation characterised by periods of both sustained retreat and minor readvance. Variations in the pattern of recession across the Wicklow Mountains are evident and appear to be influenced, in part, by topographic controls (e.g. slope, aspect, glacier hypsometry). In summary, this research establishes a relative chronology of glacial events in the region during the LGIT and presents constraints on <span class="hlt">ice</span> <span class="hlt">mass</span> extent, dynamics and retreat patterns, offering an insight into small <span class="hlt">ice</span> <span class="hlt">mass</span> behaviour in a warming climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3997805','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3997805"><span>Marine <span class="hlt">ice</span> regulates the future stability of a large Antarctic <span class="hlt">ice</span> shelf</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kulessa, Bernd; Jansen, Daniela; Luckman, Adrian J.; King, Edward C.; Sammonds, Peter R.</p> <p>2014-01-01</p> <p>The collapses of the Larsen A and B <span class="hlt">ice</span> shelves on the Antarctic Peninsula in 1995 and 2002 confirm the impact of southward-propagating climate warming in this region. Recent <span class="hlt">mass</span> and dynamic changes of Larsen B’s southern neighbour Larsen C, the fourth largest <span class="hlt">ice</span> shelf in Antarctica, may herald a similar instability. Here, using a validated <span class="hlt">ice</span>-shelf model run in diagnostic mode, constrained by satellite and in situ geophysical data, we identify the nature of this potential instability. We demonstrate that the present-day spatial distribution and orientation of the principal stresses within Larsen C <span class="hlt">ice</span> shelf are akin to those within pre-collapse Larsen B. When Larsen B’s stabilizing frontal portion was lost in 1995, the unstable remaining shelf accelerated, crumbled and ultimately collapsed. We hypothesize that Larsen C <span class="hlt">ice</span> shelf may suffer a similar fate if it were not stabilized by warm and mechanically soft marine <span class="hlt">ice</span>, entrained within narrow suture zones. PMID:24751641</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MNRAS.475.2891D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MNRAS.475.2891D"><span>GAMA/G10-COSMOS/3D-HST: the 0 < z < 5 cosmic star formation history, stellar-<span class="hlt">mass</span>, and dust-<span class="hlt">mass</span> <span class="hlt">densities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Driver, Simon P.; Andrews, Stephen K.; da Cunha, Elisabete; Davies, Luke J.; Lagos, Claudia; Robotham, Aaron S. G.; Vinsen, Kevin; Wright, Angus H.; Alpaslan, Mehmet; Bland-Hawthorn, Joss; Bourne, Nathan; Brough, Sarah; Bremer, Malcolm N.; Cluver, Michelle; Colless, Matthew; Conselice, Christopher J.; Dunne, Loretta; Eales, Steve A.; Gomez, Haley; Holwerda, Benne; Hopkins, Andrew M.; Kafle, Prajwal R.; Kelvin, Lee S.; Loveday, Jon; Liske, Jochen; Maddox, Steve J.; Phillipps, Steven; Pimbblet, Kevin; Rowlands, Kate; Sansom, Anne E.; Taylor, Edward; Wang, Lingyu; Wilkins, Stephen M.</p> <p>2018-04-01</p> <p>We use the energy-balance code MAGPHYS to determine stellar and dust <span class="hlt">masses</span>, and dust corrected star formation rates for over 200 000 GAMA galaxies, 170 000 G10-COSMOS galaxies, and 200 000 3D-HST galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous data set spanning a broad range in stellar-<span class="hlt">mass</span> (108-1012 M⊙), dust-<span class="hlt">mass</span> (106-109 M⊙), and star formation rates (0.01-100 M⊙yr-1), and over a broad redshift range (0.0 < z < 5.0). We combine these data to measure the cosmic star formation history (CSFH), the stellar-<span class="hlt">mass</span> <span class="hlt">density</span> (SMD), and the dust-<span class="hlt">mass</span> <span class="hlt">density</span> (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous data set using consistent <span class="hlt">mass</span> and star formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our CSFH we precisely reproduce the SMD with an interstellar medium replenishment factor of 0.50 ± 0.07, consistent with our choice of Chabrier initial <span class="hlt">mass</span> function plus some modest amount of stripped stellar <span class="hlt">mass</span>. Exploring the cosmic dust <span class="hlt">density</span> evolution, we find a gradual increase in dust <span class="hlt">density</span> with lookback time. We build a simple phenomenological model from the CSFH to account for the dust-<span class="hlt">mass</span> evolution, and infer two key conclusions: (1) For every unit of stellar <span class="hlt">mass</span> which is formed 0.0065-0.004 units of dust <span class="hlt">mass</span> is also formed. (2) Over the history of the Universe approximately 90-95 per cent of all dust formed has been destroyed and/or ejected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C11B0907M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C11B0907M"><span>Dating of 30m <span class="hlt">ice</span> cores drilled by Japanese Antarctic Research Expedition and environmental change study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Motoyama, H.; Suzuki, T.; Fukui, K.; Ohno, H.; Hoshina, Y.; Hirabayashi, M.; Fujita, S.</p> <p>2017-12-01</p> <p>1. Introduction It is possible to reveal the past climate and environmental change from the <span class="hlt">ice</span> core drilled in polar <span class="hlt">ice</span> sheet and glaciers. The 54th Japanese Antarctic Research Expedition conducted several shallow core drillings up to 30 m depth in the inland and coastal areas of the East Antarctic <span class="hlt">ice</span> sheet. <span class="hlt">Ice</span> core sample was cut out at a thickness of about 5 cm in the cold room of the National Institute of Polar Research, and analyzed ion, water isotope, dust and so one. We also conducted dielectric profile measurement (DEP measurement). The age as a key layer of large-scale volcanic explosion was based on Sigl et al. (Nature Climate Change, 2014). 2. Inland <span class="hlt">ice</span> core <span class="hlt">Ice</span> cores were collected at the NDF site (77°47'14"S, 39°03'34"E, 3754 m.a.s.l.) and S80 site (80°00'00"S, 40°30'04"E, 3622 m.a.s.l.). Dating of <span class="hlt">ice</span> core was done as follows. Calculate water equivalent from core <span class="hlt">density</span>. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. We determined the key layer with nssSO42 - peak corresponding to several large volcanic explosions. The accumulation rate was kept constant between the key layers. As a result, NDF was estimated to be around 1360 AD and S80 was estimated to be around 1400 AD in the deepest <span class="hlt">ice</span> core. 3. Coastal <span class="hlt">ice</span> core An <span class="hlt">ice</span> core was collected at coastal H15 sites (69°04'10"S, 40°44'51"E, 1030 m.a.s.l.). Dating of <span class="hlt">ice</span> core was done as follows. Calculate water equivalent from <span class="hlt">ice</span> core <span class="hlt">density</span>. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. Basically we decided to summer (December) and winter (June) due to the seasonal change of the water isotope (δD or δ18O). In addition to the seasonal change of isotope, confirm the following. Maximum of SO42- / Na +, which is earlier in time than the maximum of water isotope. Maximum of MSA at about the same time as the maximum of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870009722&hterms=spectrophotometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dspectrophotometry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870009722&hterms=spectrophotometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dspectrophotometry"><span>Ultraviolet spectrophotometry of comet Giacobini-Zinner during the <span class="hlt">ICE</span> encounter. [International Cometary Explorer (<span class="hlt">ICE</span>)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahearn, Michael F.; Mcfadden, Lucy A.; Feldman, Paul D.; Boehnhardt, Hermann; Rahe, Juergen; Festou, Michael; Brandt, John C.; Maran, Stephen P.; Niedner, Malcom B.; Smith, Andrew M.</p> <p>1986-01-01</p> <p>The IUE spectrophotometry of Comet P/Giacobini-Zinner was acquired in support of the International Cometary Explorer (<span class="hlt">ICE</span>) mission. The abundances (or upper limits) of UV-active species were calculated. During the <span class="hlt">ICE</span> encounter the H2O production rate was 3 times 10 to the 28th power/sec, + or - 50%, consistent with values derived from the <span class="hlt">ICE</span> experiments. Comparison of the abundance of CO2(+) ions with the total electron <span class="hlt">density</span> measured by the plasma electron experiment on <span class="hlt">ICE</span> indicates a deficiency of ions relative to electrons indicating a population of ions not detected by remote sensing. The absence of detectable Mg(+) rules out this species as a possible ion of M/Q = 24 detected by the Ion Composition Instrument, part of the <span class="hlt">ICE</span> complement of instruments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791593','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791593"><span>The future of <span class="hlt">ice</span> sheets and sea <span class="hlt">ice</span>: Between reversible retreat and unstoppable loss</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Notz, Dirk</p> <p>2009-01-01</p> <p>We discuss the existence of cryospheric “tipping points” in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea <span class="hlt">ice</span> and the retreat of <span class="hlt">ice</span> sheets: Once these <span class="hlt">ice</span> <span class="hlt">masses</span> have shrunk below an anticipated critical extent, the ice–albedo feedback might lead to the irreversible and unstoppable loss of the remaining <span class="hlt">ice</span>. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea <span class="hlt">ice</span>. Hence, in a cooler climate, sea <span class="hlt">ice</span> could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea <span class="hlt">ice</span> might largely be a consequence of a slow shift in <span class="hlt">ice</span>-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-<span class="hlt">ice</span> extent. This variability will render seasonal forecasts of the Arctic summer sea-<span class="hlt">ice</span> extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea <span class="hlt">ice</span>, a tipping point is more likely to exist for the loss of the Greenland <span class="hlt">ice</span> sheet and the West Antarctic <span class="hlt">ice</span> sheet. PMID:19884496</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMMR13A1698A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMMR13A1698A"><span>The <span class="hlt">ice</span> VII-<span class="hlt">ice</span> X phase transition with implications for planetary interiors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aarestad, B.; Frank, M. R.; Scott, H.; Bricker, M.; Prakapenka, V.</p> <p>2008-12-01</p> <p>A significant amount of research on the high pressure polymorphs of H2O have detailed the lattice structure and <span class="hlt">density</span> of these phases, namely <span class="hlt">ice</span> VI, <span class="hlt">ice</span> VII, and <span class="hlt">ice</span> X. These high pressure <span class="hlt">ices</span> are noteworthy as they may comprise a considerable part of the interior of large icy planets and satellites. However, there is a dearth of data on how the incorporation of an impurity, charged or non-charged, affects the <span class="hlt">ice</span> VII-<span class="hlt">ice</span> X transition. This study examined the <span class="hlt">ice</span> VII-<span class="hlt">ice</span> X transition that occurs at approximately 62 GPa with a pure system and two select impure systems. Solutions of pure H2O, 1.6 mole percent NaCl in H2O, and 1.60 mole percent CH3OH in H2O were compressed in a diamond anvil cell (DAC). The experiments were performed at the GSECARS 13-BM-D beam line at the Advanced Photon Source at Argonne National Laboratory. Powder diffraction data of the <span class="hlt">ice</span> samples were collected using monochromatic X-ray radiation, 0.2755 Å, and a MAR 345 online imaging system at intervals of approximately 2 GPa up to ~71.5, ~74.5, and ~68 GPa, respectively. Analyses of the data provided volume-pressure relations (at 298 K) which were used to detail the <span class="hlt">ice</span> VII-<span class="hlt">ice</span> X phase transition. The pressure of the phase transition, based upon an interpretation of the X-ray diffraction data, was found to vary as a function of the impurity type. Thus, the depth of the <span class="hlt">ice</span> VII-<span class="hlt">ice</span> X phase transition within an <span class="hlt">ice</span>-rich planetary body can be influenced by trace-level impurities.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C23E0542F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C23E0542F"><span>Validation and Interpretation of a New Sea <span class="hlt">Ice</span> Globice Dataset Using Buoys and the Cice Sea <span class="hlt">Ice</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flocco, D.; Laxon, S. W.; Feltham, D. L.; Haas, C.</p> <p>2011-12-01</p> <p>The Glob<span class="hlt">Ice</span> project has provided high resolution sea <span class="hlt">ice</span> product datasets over the Arctic derived from SAR data in the ESA archive. The products are validated sea <span class="hlt">ice</span> motion, deformation and fluxes through straits. Glob<span class="hlt">Ice</span> sea <span class="hlt">ice</span> velocities, deformation data and sea <span class="hlt">ice</span> concentration have been validated using buoy data provided by the International Arctic Buoy Program (IABP). Over 95% of the Glob<span class="hlt">Ice</span> and buoy data analysed fell within 5 km of each other. The Glob<span class="hlt">Ice</span> Eulerian image pair product showed a high correlation with buoy data. The sea <span class="hlt">ice</span> concentration product was compared to SSM/I data. An evaluation of the validity of the Glob<span class="hlt">ICE</span> data will be presented in this work. Glob<span class="hlt">ICE</span> sea <span class="hlt">ice</span> velocity and deformation were compared with runs of the CICE sea <span class="hlt">ice</span> model: in particular the <span class="hlt">mass</span> fluxes through the straits were used to investigate the correlation between the winter behaviour of sea <span class="hlt">ice</span> and the sea <span class="hlt">ice</span> state in the following summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...565A..24F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...565A..24F"><span>On the probability distribution function of the <span class="hlt">mass</span> surface <span class="hlt">density</span> of molecular clouds. I</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischera, Jörg</p> <p>2014-05-01</p> <p>The probability distribution function (PDF) of the <span class="hlt">mass</span> surface <span class="hlt">density</span> is an essential characteristic of the structure of molecular clouds or the interstellar medium in general. Observations of the PDF of molecular clouds indicate a composition of a broad distribution around the maximum and a decreasing tail at high <span class="hlt">mass</span> surface <span class="hlt">densities</span>. The first component is attributed to the random distribution of gas which is modeled using a log-normal function while the second component is attributed to condensed structures modeled using a simple power-law. The aim of this paper is to provide an analytical model of the PDF of condensed structures which can be used by observers to extract information about the condensations. The condensed structures are considered to be either spheres or cylinders with a truncated radial <span class="hlt">density</span> profile at cloud radius rcl. The assumed profile is of the form ρ(r) = ρc/ (1 + (r/r0)2)n/ 2 for arbitrary power n where ρc and r0 are the central <span class="hlt">density</span> and the inner radius, respectively. An implicit function is obtained which either truncates (sphere) or has a pole (cylinder) at maximal <span class="hlt">mass</span> surface <span class="hlt">density</span>. The PDF of spherical condensations and the asymptotic PDF of cylinders in the limit of infinite overdensity ρc/ρ(rcl) flattens for steeper <span class="hlt">density</span> profiles and has a power law asymptote at low and high <span class="hlt">mass</span> surface <span class="hlt">densities</span> and a well defined maximum. The power index of the asymptote Σ- γ of the logarithmic PDF (ΣP(Σ)) in the limit of high <span class="hlt">mass</span> surface <span class="hlt">densities</span> is given by γ = (n + 1)/(n - 1) - 1 (spheres) or by γ = n/ (n - 1) - 1 (cylinders in the limit of infinite overdensity). Appendices are available in electronic form at http://www.aanda.org</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29872048','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29872048"><span>Mapping uncharted territory in <span class="hlt">ice</span> from zeolite networks to <span class="hlt">ice</span> structures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Engel, Edgar A; Anelli, Andrea; Ceriotti, Michele; Pickard, Chris J; Needs, Richard J</p> <p>2018-06-05</p> <p><span class="hlt">Ice</span> is one of the most extensively studied condensed matter systems. Yet, both experimentally and theoretically several new phases have been discovered over the last years. Here we report a large-scale <span class="hlt">density</span>-functional-theory study of the configuration space of water <span class="hlt">ice</span>. We geometry optimise 74,963 <span class="hlt">ice</span> structures, which are selected and constructed from over five million tetrahedral networks listed in the databases of Treacy, Deem, and the International Zeolite Association. All prior knowledge of <span class="hlt">ice</span> is set aside and we introduce "generalised convex hulls" to identify configurations stabilised by appropriate thermodynamic constraints. We thereby rediscover all known phases (I-XVII, i, 0 and the quartz phase) except the metastable <span class="hlt">ice</span> IV. Crucially, we also find promising candidates for <span class="hlt">ices</span> XVIII through LI. Using the "sketch-map" dimensionality-reduction algorithm we construct an a priori, navigable map of configuration space, which reproduces similarity relations between structures and highlights the novel candidates. By relating the known phases to the tractably small, yet structurally diverse set of synthesisable candidate structures, we provide an excellent starting point for identifying formation pathways.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC23D1173L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC23D1173L"><span>Sparse <span class="hlt">ice</span>: Geophysical, biological and Indigenous knowledge perspectives on a habitat for <span class="hlt">ice</span>-associated fauna</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, O. A.; Eicken, H.; Weyapuk, W., Jr.; Adams, B.; Mohoney, A. R.</p> <p>2015-12-01</p> <p>The significance of highly dispersed, remnant Arctic sea <span class="hlt">ice</span> as a platform for marine mammals and indigenous hunters in spring and summer may have increased disproportionately with changes in the <span class="hlt">ice</span> cover. As dispersed remnant <span class="hlt">ice</span> becomes more common in the future it will be increasingly important to understand its ecological role for upper trophic levels such as marine mammals and its role for supporting primary productivity of <span class="hlt">ice</span>-associated algae. Potential sparse <span class="hlt">ice</span> habitat at sea <span class="hlt">ice</span> concentrations below 15% is difficult to detect using remote sensing data alone. A combination of high resolution satellite imagery (including Synthetic Aperture Radar), data from the Barrow sea <span class="hlt">ice</span> radar, and local observations from indigenous sea <span class="hlt">ice</span> experts was used to detect sparse sea <span class="hlt">ice</span> in the Alaska Arctic. Traditional knowledge on sea <span class="hlt">ice</span> use by marine mammals was used to delimit the scales where sparse <span class="hlt">ice</span> could still be used as habitat for seals and walrus. Potential sparse <span class="hlt">ice</span> habitat was quantified with respect to overall spatial extent, size of <span class="hlt">ice</span> floes, and <span class="hlt">density</span> of floes. Sparse <span class="hlt">ice</span> persistence offshore did not prevent the occurrence of large coastal walrus haul outs, but the lack of sparse <span class="hlt">ice</span> and early sea <span class="hlt">ice</span> retreat coincided with local observations of ringed seal pup mortality. Observations from indigenous hunters will continue to be an important source of information for validating remote sensing detections of sparse <span class="hlt">ice</span>, and improving understanding of marine mammal adaptations to sea <span class="hlt">ice</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33C0838L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33C0838L"><span>Deglaciation-induced uplift of the Petermann glacier <span class="hlt">ice</span> margin observed with InSAR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Q.; Amelung, F.; Wdowinski, S.</p> <p>2016-12-01</p> <p>The Greenland <span class="hlt">ice</span> sheet is rapidly shrinking with the fastest retreat and thinning occurring at the <span class="hlt">ice</span> sheet margin and near the outlet glaciers. The changes of the <span class="hlt">ice</span> <span class="hlt">mass</span> cause an elastic response of the bedrock. <span class="hlt">Ice</span> <span class="hlt">mass</span> loss during the summer months is associated with uplift, whereas <span class="hlt">ice</span> <span class="hlt">mass</span> increase during the winter months is associated with subsidence.The German TerraSAR-X and TanDEM-X satellites have systematically observed selected sites along the Greenland Petermann <span class="hlt">ice</span> sheet margin since summer 2012. Here we present ground deformation observations obtained using an InSAR time-series approach based on small baseline interferograms. We observed rapid deglaciation-induced uplift on naked bedrock near the Petermann glacier <span class="hlt">ice</span> margin Deformation observed by InSAR is consistent with GPS vertical observations. The time series displacement data reveal not only net uplift but also the seasonal variations. There is no strong relative between displacement changes and SMB <span class="hlt">ice</span> <span class="hlt">mass</span> change. The seasonal variations in local area may caused by both nearby SMB changes and <span class="hlt">ice</span> dynamic changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A33M..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A33M..02W"><span>Upper-Tropospheric Cloud <span class="hlt">Ice</span> from <span class="hlt">Ice</span>Cube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, D. L.</p> <p>2017-12-01</p> <p>Cloud <span class="hlt">ice</span> plays important roles in Earth's energy budget and cloud-precipitation processes. Knowledge of global cloud <span class="hlt">ice</span> and its properties is critical for understanding and quantifying its roles in Earth's atmospheric system. It remains a great challenge to measure these variables accurately from space. Submillimeter (submm) wave remote sensing has capability of penetrating clouds and measuring <span class="hlt">ice</span> <span class="hlt">mass</span> and microphysical properties. In particular, the 883-GHz frequency is a highest spectral window in microwave frequencies that can be used to fill a sensitivity gap between thermal infrared (IR) and mm-wave sensors in current spaceborne cloud <span class="hlt">ice</span> observations. <span class="hlt">Ice</span>Cube is a cubesat spaceflight demonstration of 883-GHz radiometer technology. Its primary objective is to raise the technology readiness level (TRL) of 883-GHz cloud radiometer for future Earth science missions. By flying a commercial receiver on a 3U cubesat, <span class="hlt">Ice</span>Cube is able to achieve fast-track maturation of space technology, by completing its development, integration and testing in 2.5 years. <span class="hlt">Ice</span>Cube was successfully delivered to ISS in April 2017 and jettisoned from the International Space Station (ISS) in May 2017. The <span class="hlt">Ice</span>Cube cloud-<span class="hlt">ice</span> radiometer (ICIR) has been acquiring data since the jettison on a daytime-only operation. <span class="hlt">Ice</span>Cube adopted a simple design without payload mechanism. It makes maximum utilization of solar power by spinning the spacecraft continuously about the Sun vector at a rate of 1.2° per second. As a result, the ICIR is operated under the limited resources (8.6 W without heater) and largely-varying (18°C-28°C) thermal environments. The spinning cubesat also allows ICIR to have periodical views between the Earth (atmosphere and clouds) and cold space (calibration), from which the first 883-GHz cloud map is obtained. The 883-GHz cloud radiance, sensitive to <span class="hlt">ice</span> particle scattering, is proportional to cloud <span class="hlt">ice</span> amount above 10 km. The ICIR cloud map acquired during June 20-July 2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28973875','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28973875"><span>Katabatic winds diminish precipitation contribution to the Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> balance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grazioli, Jacopo; Madeleine, Jean-Baptiste; Gallée, Hubert; Forbes, Richard M; Genthon, Christophe; Krinner, Gerhard; Berne, Alexis</p> <p>2017-10-10</p> <p>Snowfall in Antarctica is a key term of the <span class="hlt">ice</span> sheet <span class="hlt">mass</span> budget that influences the sea level at global scale. Over the continental margins, persistent katabatic winds blow all year long and supply the lower troposphere with unsaturated air. We show that this dry air leads to significant low-level sublimation of snowfall. We found using unprecedented data collected over 1 year on the coast of Adélie Land and simulations from different atmospheric models that low-level sublimation accounts for a 17% reduction of total snowfall over the continent and up to 35% on the margins of East Antarctica, significantly affecting satellite-based estimations close to the ground. Our findings suggest that, as climate warming progresses, this process will be enhanced and will limit expected precipitation increases at the ground level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Sci...341..266R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Sci...341..266R"><span><span class="hlt">Ice</span>-Shelf Melting Around Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.</p> <p>2013-07-01</p> <p>We compare the volume flux divergence of Antarctic <span class="hlt">ice</span> shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and <span class="hlt">mass</span> balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making <span class="hlt">ice</span>-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne <span class="hlt">ice</span> shelves covering two-thirds of the total <span class="hlt">ice</span>-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific <span class="hlt">ice</span> shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic <span class="hlt">ice</span> shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcSci..12..507M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcSci..12..507M"><span>Turbulent heat transfer as a control of platelet <span class="hlt">ice</span> growth in supercooled under-<span class="hlt">ice</span> ocean boundary layers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McPhee, Miles G.; Stevens, Craig L.; Smith, Inga J.; Robinson, Natalie J.</p> <p>2016-04-01</p> <p>Late winter measurements of turbulent quantities in tidally modulated flow under land-fast sea <span class="hlt">ice</span> near the Erebus Glacier Tongue, McMurdo Sound, Antarctica, identified processes that influence growth at the interface of an <span class="hlt">ice</span> surface in contact with supercooled seawater. The data show that turbulent heat exchange at the ocean-<span class="hlt">ice</span> boundary is characterized by the product of friction velocity and (negative) water temperature departure from freezing, analogous to similar results for moderate melting rates in seawater above freezing. Platelet <span class="hlt">ice</span> growth appears to increase the hydraulic roughness (drag) of fast <span class="hlt">ice</span> compared with undeformed fast <span class="hlt">ice</span> without platelets. Platelet growth in supercooled water under thick <span class="hlt">ice</span> appears to be rate-limited by turbulent heat transfer and that this is a significant factor to be considered in <span class="hlt">mass</span> transfer at the underside of <span class="hlt">ice</span> shelves and sea <span class="hlt">ice</span> in the vicinity of <span class="hlt">ice</span> shelves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22538614','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22538614"><span>Antarctic <span class="hlt">ice</span>-sheet loss driven by basal melting of <span class="hlt">ice</span> shelves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pritchard, H D; Ligtenberg, S R M; Fricker, H A; Vaughan, D G; van den Broeke, M R; Padman, L</p> <p>2012-04-25</p> <p>Accurate prediction of global sea-level rise requires that we understand the cause of recent, widespread and intensifying glacier acceleration along Antarctic <span class="hlt">ice</span>-sheet coastal margins. Atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating <span class="hlt">ice</span> shelves, potentially limiting their ability to buttress the flow of grounded tributary glaciers. Indeed, recent <span class="hlt">ice</span>-shelf collapse led to retreat and acceleration of several glaciers on the Antarctic Peninsula. But the extent and magnitude of <span class="hlt">ice</span>-shelf thickness change, the underlying causes of such change, and its link to glacier flow rate are so poorly understood that its future impact on the <span class="hlt">ice</span> sheets cannot yet be predicted. Here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum-Antarctic pattern of <span class="hlt">ice</span>-shelf thinning through increased basal melt. We deduce that this increased melt is the primary control of Antarctic <span class="hlt">ice</span>-sheet loss, through a reduction in buttressing of the adjacent <span class="hlt">ice</span> sheet leading to accelerated glacier flow. The highest thinning rates occur where warm water at depth can access thick <span class="hlt">ice</span> shelves via submarine troughs crossing the continental shelf. Wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of Antarctic <span class="hlt">ice</span> shelves, through ocean upwelling in the Amundsen and Bellingshausen seas, and atmospheric warming on the Antarctic Peninsula. This implies that climate forcing through changing winds influences Antarctic <span class="hlt">ice</span>-sheet <span class="hlt">mass</span> balance, and hence global sea level, on annual to decadal timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C53C0787S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C53C0787S"><span>Development of a multi-sensor elevation time series pole-ward of 86°S in support of altimetry validation and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Studinger, M.; Brunt, K. M.; Casey, K.; Medley, B.; Neumann, T.; Manizade, S.; Linkswiler, M. A.</p> <p>2015-12-01</p> <p>In order to produce a cross-calibrated long-term record of <span class="hlt">ice</span>-surface elevation change for input into <span class="hlt">ice</span> sheet models and <span class="hlt">mass</span> balance studies it is necessary to "link the measurements made by airborne laser altimeters, satellite measurements of ICESat, ICESat-2, and CryoSat-2" [<span class="hlt">Ice</span>Bridge Level 1 Science Requirements, 2012] and determine the biases and the spatial variations between radar altimeters and laser altimeters using different wavelengths. The convergence zones of all ICESat tracks (86°S) and all ICESat-2 and CryoSat-2 tracks (88°S) are in regions of relatively low accumulation, making them ideal for satellite altimetry calibration. In preparation for ICESat-2 validation, the <span class="hlt">Ice</span>Bridge and ICESat-2 science teams have designed <span class="hlt">Ice</span>Bridge data acquisitions around 86°S and 88°S. Several aspects need to be considered when comparing and combining elevation measurements from different radar and laser altimeters, including: a) foot print size and spatial sampling pattern; b) accuracy and precision of each data sets; c) varying signal penetration into the snow; and d) changes in geodetic reference frames over time, such as the International Terrestrial Reference Frame (ITRF). The presentation will focus on the analysis of several <span class="hlt">Ice</span>Bridge flights around 86 and 88°S with the LVIS and ATM airborne laser altimeters and will evaluate the accuracy and precision of these data sets. To properly interpret the observed elevation change (dh/dt) as <span class="hlt">mass</span> change, however, the various processes that control surface elevation fluctuations must be quantified and therefore future work will quantify the spatial variability in snow accumulation rates pole-ward of 86°S and in particular around 88°S. Our goal is to develop a cross-validated multi-sensor time series of surface elevation change pole-ward of 86°S that, in combination with measured accumulation rates, will support ICESat-2 calibration and validation and <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.718e2033R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.718e2033R"><span>Cosmic ray spectrum and composition from three years of <span class="hlt">Ice</span>Top and <span class="hlt">Ice</span>Cube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rawlins, K.; <author pre="for ">IceCube Collaboration</p> <p>2016-05-01</p> <p><span class="hlt">Ice</span>Top is the surface component of the <span class="hlt">Ice</span>Cube Observatory, composed of frozen water tanks at the top of <span class="hlt">Ice</span>Cube’s strings. Data from this detector can be analyzed in different ways with the goal of measuring cosmic ray spectrum and composition. The shower size S125 from <span class="hlt">Ice</span>Top alone can be used as a proxy for primary energy, and unfolded into an all-particle spectrum. In addition, S125 from the surface can be combined with high-energy muon energy loss information from the deep <span class="hlt">Ice</span>Cube detector for those air showers which pass through both. Using these coincident events in a complementary analysis, both the spectrum and <span class="hlt">mass</span> composition of primary cosmic rays can be extracted in parallel using a neural network. Both of these analyses have been performed on three years of <span class="hlt">Ice</span>Top and <span class="hlt">Ice</span>Cube data. Both all-particle spectra as well as individual spectra for elemental groups are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25254511','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25254511"><span>Rapid determination of cell <span class="hlt">mass</span> and <span class="hlt">density</span> using digitally controlled electric field in a microfluidic chip.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhao, Yuliang; Lai, Hok Sum Sam; Zhang, Guanglie; Lee, Gwo-Bin; Li, Wen Jung</p> <p>2014-11-21</p> <p>The <span class="hlt">density</span> of a single cell is a fundamental property of cells. Cells in the same cycle phase have similar volume, but the differences in their <span class="hlt">mass</span> and <span class="hlt">density</span> could elucidate each cell's physiological state. Here we report a novel technique to rapidly measure the <span class="hlt">density</span> and <span class="hlt">mass</span> of a single cell using an optically induced electrokinetics (OEK) microfluidic platform. Presently, single cellular <span class="hlt">mass</span> and <span class="hlt">density</span> measurement devices require a complicated fabrication process and their output is not scalable, i.e., it is extremely difficult to measure the <span class="hlt">mass</span> and <span class="hlt">density</span> of a large quantity of cells rapidly. The technique reported here operates on a principle combining sedimentation theory, computer vision, and microparticle manipulation techniques in an OEK microfluidic platform. We will show in this paper that this technique enables the measurement of single-cell volume, <span class="hlt">density</span>, and <span class="hlt">mass</span> rapidly and accurately in a repeatable manner. The technique is also scalable - it allows simultaneous measurement of volume, <span class="hlt">density</span>, and <span class="hlt">mass</span> of multiple cells. Essentially, a simple time-controlled projected light pattern is used to illuminate the selected area on the OEK microfluidic chip that contains cells to lift the cells to a particular height above the chip's surface. Then, the cells are allowed to "free fall" to the chip's surface, with competing buoyancy, gravitational, and fluidic drag forces acting on the cells. By using a computer vision algorithm to accurately track the motion of the cells and then relate the cells' motion trajectory to sedimentation theory, the volume, <span class="hlt">mass</span>, and <span class="hlt">density</span> of each cell can be rapidly determined. A theoretical model of micro-sized spheres settling towards an infinite plane in a microfluidic environment is first derived and validated experimentally using standard micropolystyrene beads to demonstrate the viability and accuracy of this new technique. Next, we show that the yeast cell volume, <span class="hlt">mass</span>, and <span class="hlt">density</span> could be rapidly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040035786&hterms=ships+location&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dships%2Blocation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040035786&hterms=ships+location&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dships%2Blocation"><span>Studies of the Antarctic Sea <span class="hlt">Ice</span> Edges and <span class="hlt">Ice</span> Extents from Satellite and Ship Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Worby, Anthony P.; Comiso, Josefino C.</p> <p>2003-01-01</p> <p>Passive-microwave derived <span class="hlt">ice</span> edge locations in Antarctica are assessed against other satellite data as well as in situ observations of <span class="hlt">ice</span> edge location made between 1989 and 2000. The passive microwave data generally agree with satellite and ship data but the <span class="hlt">ice</span> concentration at the observed <span class="hlt">ice</span> edge varies greatly with averages of 14% for the TEAM algorithm and 19% for the Bootstrap algorithm. The comparisons of passive microwave with the field data show that in the <span class="hlt">ice</span> growth season (March - October) the agreement is extremely good, with r(sup 2) values of 0.9967 and 0.9797 for the Bootstrap and TEAM algorithms respectively. In the melt season however (November - February) the passive microwave <span class="hlt">ice</span> edge is typically 1-2 degrees south of the observations due to the low concentration and saturated nature of the <span class="hlt">ice</span>. Sensitivity studies show that these results can have significant impact on trend and <span class="hlt">mass</span> balance studies of the sea <span class="hlt">ice</span> cover in the Southern Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4371949','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4371949"><span>Ocean-driven thinning enhances iceberg calving and retreat of Antarctic <span class="hlt">ice</span> shelves</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Yan; Moore, John C.; Cheng, Xiao; Gladstone, Rupert M.; Bassis, Jeremy N.; Liu, Hongxing; Wen, Jiahong; Hui, Fengming</p> <p>2015-01-01</p> <p>Iceberg calving from all Antarctic <span class="hlt">ice</span> shelves has never been directly measured, despite playing a crucial role in <span class="hlt">ice</span> sheet <span class="hlt">mass</span> balance. Rapid changes to iceberg calving naturally arise from the sporadic detachment of large tabular bergs but can also be triggered by climate forcing. Here we provide a direct empirical estimate of <span class="hlt">mass</span> loss due to iceberg calving and melting from Antarctic <span class="hlt">ice</span> shelves. We find that between 2005 and 2011, the total <span class="hlt">mass</span> loss due to iceberg calving of 755 ± 24 gigatonnes per year (Gt/y) is only half the total loss due to basal melt of 1516 ± 106 Gt/y. However, we observe widespread retreat of <span class="hlt">ice</span> shelves that are currently thinning. Net <span class="hlt">mass</span> loss due to iceberg calving for these <span class="hlt">ice</span> shelves (302 ± 27 Gt/y) is comparable in magnitude to net <span class="hlt">mass</span> loss due to basal melt (312 ± 14 Gt/y). Moreover, we find that iceberg calving from these decaying <span class="hlt">ice</span> shelves is dominated by frequent calving events, which are distinct from the less frequent detachment of isolated tabular icebergs associated with <span class="hlt">ice</span> shelves in neutral or positive <span class="hlt">mass</span> balance regimes. Our results suggest that thinning associated with ocean-driven increased basal melt can trigger increased iceberg calving, implying that iceberg calving may play an overlooked role in the demise of shrinking <span class="hlt">ice</span> shelves, and is more sensitive to ocean forcing than expected from steady state calving estimates. PMID:25733856</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/985693','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/985693"><span>Method for detecting a <span class="hlt">mass</span> <span class="hlt">density</span> image of an object</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Wernick, Miles N [Chicago, IL; Yang, Yongyi [Westmont, IL</p> <p>2008-12-23</p> <p>A method for detecting a <span class="hlt">mass</span> <span class="hlt">density</span> image of an object. An x-ray beam is transmitted through the object and a transmitted beam is emitted from the object. The transmitted beam is directed at an angle of incidence upon a crystal analyzer. A diffracted beam is emitted from the crystal analyzer onto a detector and digitized. A first image of the object is detected from the diffracted beam emitted from the crystal analyzer when positioned at a first angular position. A second image of the object is detected from the diffracted beam emitted from the crystal analyzer when positioned at a second angular position. A refraction image is obtained and a regularized mathematical inversion algorithm is applied to the refraction image to obtain a <span class="hlt">mass</span> <span class="hlt">density</span> image.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991Metro..28...45G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991Metro..28...45G"><span>Experimental Determination of Air <span class="hlt">Density</span> Using a 1 kg <span class="hlt">Mass</span> Comparator in Vacuum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gläser, M.; Schwartz, R.; Mecke, M.</p> <p>1991-01-01</p> <p>The <span class="hlt">density</span> of ambient air has been determined by a straightforward experimental method. The apparent <span class="hlt">masses</span> of two artefacts having about the same <span class="hlt">mass</span> and surface, but different well-known volumes, have been compared by using a 1 kg balance in vacuum and in air. The differences of apparent <span class="hlt">masses</span> and volumes yield the air <span class="hlt">density</span> with a relative uncertainty (1σ) of 5 × 10-5. From measurements made using a third artefact, surface sorption effects caused by the change between vacuum and air conditions gave a coefficient of about 0,2 μg cm-2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914046W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914046W"><span>Bayesian inference of <span class="hlt">ice</span> thickness from remote-sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Werder, Mauro A.; Huss, Matthias</p> <p>2017-04-01</p> <p>Knowledge about <span class="hlt">ice</span> thickness and volume is indispensable for studying <span class="hlt">ice</span> dynamics, future sea-level rise due to glacier melt or their contribution to regional hydrology. Accurate measurements of glacier thickness require on-site work, usually employing radar techniques. However, these field measurements are time consuming, expensive and sometime downright impossible. Conversely, measurements of the <span class="hlt">ice</span> surface, namely elevation and flow velocity, are becoming available world-wide through remote sensing. The model of Farinotti et al. (2009) calculates <span class="hlt">ice</span> thicknesses based on a <span class="hlt">mass</span> conservation approach paired with shallow <span class="hlt">ice</span> physics using estimates of the surface <span class="hlt">mass</span> balance. The presented work applies a Bayesian inference approach to estimate the parameters of a modified version of this forward model by fitting it to both measurements of surface flow speed and of <span class="hlt">ice</span> thickness. The inverse model outputs <span class="hlt">ice</span> thickness as well the distribution of the error. We fit the model to ten test glaciers and <span class="hlt">ice</span> caps and quantify the improvements of thickness estimates through the usage of surface <span class="hlt">ice</span> flow measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B7..585X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B7..585X"><span>Extraction of <span class="hlt">Ice</span> Sheet Layers from Two Intersected Radar Echograms Near Neem <span class="hlt">Ice</span> Core in Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, S.; Muller, J.-P.</p> <p>2016-06-01</p> <p>Accumulation of snow and <span class="hlt">ice</span> over time result in <span class="hlt">ice</span> sheet layers. These can be remotely sensed where there is a contrast in electromagnetic properties, which reflect variations of the <span class="hlt">ice</span> <span class="hlt">density</span>, acidity and fabric orientation. Internal <span class="hlt">ice</span> layers are assumed to be isochronous, deep beneath the <span class="hlt">ice</span> surface, and parallel to the direction of <span class="hlt">ice</span> flow. The distribution of internal layers is related to <span class="hlt">ice</span> sheet dynamics, such as the basal melt rate, basal elevation variation and changes in <span class="hlt">ice</span> flow mode, which are important parameters to model the <span class="hlt">ice</span> sheet. Radar echo sounder is an effective instrument used to study the sedimentology of the Earth and planets. <span class="hlt">Ice</span> Penetrating Radar (IPR) is specific kind of radar echo sounder, which extends studies of <span class="hlt">ice</span> sheets from surface to subsurface to deep internal <span class="hlt">ice</span> sheets depending on the frequency utilised. In this study, we examine a study site where folded <span class="hlt">ice</span> occurs in the internal <span class="hlt">ice</span> sheet south of the North Greenland Eemian <span class="hlt">ice</span> drilling (NEEM) station, where two intersected radar echograms acquired by the Multi-channel Coherent Radar Depth Sounder (MCoRDS) employed in the NASA's Operation <span class="hlt">Ice</span>Bridge (OIB) mission imaged this folded <span class="hlt">ice</span>. We propose a slice processing flow based on a Radon Transform to trace and extract these two sets of curved <span class="hlt">ice</span> sheet layers, which can then be viewed in 3-D, demonstrating the 3-D structure of the <span class="hlt">ice</span> folds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980151107','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980151107"><span>West-Antarctic <span class="hlt">Ice</span> Streams: Analog to <span class="hlt">Ice</span> Flow in Channels on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lucchitta, B. K.</p> <p>1997-01-01</p> <p>Sounding of the sea floor in front of the Ross <span class="hlt">Ice</span> Shelf in Antarctica recently revealed large persistent patterns of longitudinal megaflutes and drumlinoid forms, which are interpreted to have formed at the base of <span class="hlt">ice</span> streams during the list glacial advance. The flutes bear remarkable resemblance to longitudinal grooves and highly elongated streamlined islands found on the floors of some large martian channels, called outflow channels. ln addition, other similarities exist between Antarctic <span class="hlt">ice</span> streams and outflow channels. <span class="hlt">Ice</span> streams are 30 to 80 km wide and hundreds of kilometers long, as are the martian channels. <span class="hlt">Ice</span> stream beds are below sea level. Floors of many martian outflow channels lie below martian datum, which may have been close to or below past martian sea levels. The Antarctic <span class="hlt">ice</span> stream bed gradient is flat and locally may go uphill, and surface slopes are exceptionally low. So are gradients of martian channels. The depth to the bed in <span class="hlt">ice</span> streams is 1 to 1.5 km. At bankful stage, the depth of the fluid in outflow channels would have been 1 to 2 km. These similarities suggest that the martian outflow channels, whose origin is commonly attributed to gigantic catastrophic floods, were locally filled by <span class="hlt">ice</span> that left a conspicuous morphologic imprint. Unlike the West-Antarctic-<span class="hlt">ice</span> streams, which discharge <span class="hlt">ice</span> from an <span class="hlt">ice</span> sheet, <span class="hlt">ice</span> in the martian channels came from water erupting from the ground. In the cold martian environment, this water, if of moderate volume, would eventually freeze. Thus it may have formed <span class="hlt">icings</span> on springs, <span class="hlt">ice</span> dams and jams on constrictions in the channel path, or frozen pools. Given sufficient thickness and downhill surface gradient, these <span class="hlt">ice</span> <span class="hlt">masses</span> would have moved; and given the right conditions, they could have moved like Antarctic <span class="hlt">ice</span> streams.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17733504','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17733504"><span>Devon island <span class="hlt">ice</span> cap: core stratigraphy and paleoclimate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koerner, R M</p> <p>1977-04-01</p> <p>Valuable paleoclimatic information can be gained by studying the distribution of melt layers in deep <span class="hlt">ice</span> cores. A profile representing the percentage of <span class="hlt">ice</span> in melt layers in a core drilled from the Devon Island <span class="hlt">ice</span> cap plotted against both time and depth shows that the <span class="hlt">ice</span> cap has experienced a period of very warm summers since 1925, following a period of colder summers between about 1600 and 1925. The earlier period was coldest between 1680 and 1730. There is a high correlation between the melt-layer <span class="hlt">ice</span> percentage and the <span class="hlt">mass</span> balance of the <span class="hlt">ice</span> cap. The relation between them suggests that the <span class="hlt">ice</span> cap <span class="hlt">mass</span> balance was zero (accumulation equaled ablation) during the colder period but is negative in the present warmer one. There is no firm evidence of a present cooling trend in the summer conditions on the <span class="hlt">ice</span> cap. A comparison with the melt-layer <span class="hlt">ice</span> percentage in cores from the other major Canadian Arctic <span class="hlt">ice</span> caps shows that the variation of summer conditions found for the Devon Island <span class="hlt">ice</span> cap is representative for all the large <span class="hlt">ice</span> caps for about 90 percent of the time. There is also a good correlation between melt-layer percentage and summer sea-<span class="hlt">ice</span> conditions in the archipelago. This suggests that the search for the northwest passage was influenced by changing climate, with the 19th-century peak of the often tragic exploration coinciding with a period of very cold summers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008cosp...37.1090G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37.1090G"><span>Fireballs <span class="hlt">Masses</span> and <span class="hlt">Densities</span>: Hypotheses and Reality</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gritsevich, Maria</p> <p></p> <p>Techniques of determining the <span class="hlt">masses</span> of meteor bodies have long been discussed in the literature dedicated to meteor studies. Unfortunately the development of methods for evaluating meteors and fireballs parameters from observational data requires much attention since the available literature, including handbooks (e.g., C. W. Allen, Astrophysical Quantities, Athlone, London, 1973), contains discrepancies that are of a basic character rather than due to experimental uncertainties. A comprehensive survey and analysis deserve a separate publication. Thus, we will cite here some literary sources. The <span class="hlt">mass</span> of a fireball is conventionally determined using a photometric formula, by integrating the brightness along the entire luminous segment of the trajectory. The <span class="hlt">mass</span> can also be estimated using the altitude and rate of fireball deceleration in the atmosphere. The discrepancy of the estimates obtained using these two techniques is usually diminished by selecting "appropriate" values of the fireball <span class="hlt">density</span>. However, this leads to obviously underestimated values of 0.25 g/cm3 for this <span class="hlt">density</span>. In order to eliminate these discrepancies, it was proposed to consider a swarm of similar-size fragments instead of a single meteoroid. In this case, it is the photometric-to-dynamic <span class="hlt">mass</span> ratio that determines the number of such fragments. In the present report, the <span class="hlt">mass</span> is calculated using the data of actual observations, by selecting the parameters describing deceleration and ablation of fireballs along the luminous segment of the trajectory. New model is based on the best fitting of the observational data by an analytical solution of the equations of meteor physics. In doing so, the author tried to take into account all of the peculiarities of the events noted in the literature, as well as the newest results of numerical experiments on the 3D aerodynamics of bodies of complicated shapes. The proximity of results obtained using different dynamic methods implies that observational</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMED13B0590H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMED13B0590H"><span><span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby: A Program for Sustained, Classroom-Based K-8 Teacher Professional Development</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamilton, C.</p> <p>2009-12-01</p> <p><span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby is a K-8 science program created by the education team at the Center for the Remote Sensing of <span class="hlt">Ice</span> Sheets (CReSIS), an NSF-funded science and technology center headquartered at the University of Kansas. The twenty-four hands-on activities, which constitute the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby curriculum, were developed to help students understand the role of polar <span class="hlt">ice</span> sheets in sea level rise. These activities, presented in classrooms by CReSIS' Educational Outreach Coordinator, demonstrate many of the scientific properties of <span class="hlt">ice</span>, including displacement and <span class="hlt">density</span>. Student journals are utilized with each lesson as a strategy for improving students' science process skills. Journals also help the instructor identify misconceptions, assess comprehension, and provide students with a year-long science reference log. Pre- and post- assessments are given to both teachers and students before and after the program, providing data for evaluation and improvement of the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby program. While students are actively engaged in hands-on learning about the unusual topics of <span class="hlt">ice</span> sheets, glaciers, icebergs and sea <span class="hlt">ice</span>, the CReSIS' Educational Coordinator is able to model best practices in science education, such as questioning and inquiry-based methods of instruction. In this way, the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby program also serves as ongoing, in-class, professional development for teachers. Teachers are also provided supplemental activities to do with their classes between CReSIS' visits to encourage additional science lessons, reinforce concepts taught in the <span class="hlt">Ice</span>, <span class="hlt">Ice</span>, Baby program, and to foster teachers' progression toward more reform-based science instruction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992JGR....9720325W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992JGR....9720325W"><span>Relationship between sea <span class="hlt">ice</span> freeboard and draft in the Arctic Basin, and implications for <span class="hlt">ice</span> thickness monitoring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wadhams, P.; Tucker, W. B.; Krabill, W. B.; Swift, R. N.; Comiso, J. C.; Davis, N. R.</p> <p>1992-12-01</p> <p>We have confirmed our earlier finding that the probability <span class="hlt">density</span> function (pdf) of <span class="hlt">ice</span> freeboard in the Arctic Ocean can be converted to a pdf of <span class="hlt">ice</span> draft by applying a simple coordinate transformation based on the measured mean draft and mean elevation. This applies in each of six 50-km sections (north of Greenland) of joint airborne laser and submarine sonar profile obtained along nearly coincident tracks from the Arctic Basin north of Greenland and tested for this study. Detailed differences in the shape of the pdf can be explained on the basis of snow load and can, in principle, be compensated by the use of a more sophisticated freeboard-dependent transformation. The measured "<span class="hlt">density</span> ratio" R (actually mean draft/mean elevation ratio) for each section was found to be consistent over all sections tested, despite differences in the <span class="hlt">ice</span> regime, indicating that a single value of R might be used for measurements done in this season of the year. The mean value <R> from all six sections is 7.89; on the assumption that all six values are drawn from the same population, the standard deviation is 0.55 for a single 50-km section, and thus 0.22 for 300 km of track. In attempting to infer <span class="hlt">ice</span> draft from laser-measured freeboard, we would therefore expect an accuracy of about ±28 cm in 50 km of track (if mean draft is about 4 m) and about ±11 cm in 300 km of track; these accuracies are compatible with the resolution of predictions from numerical models. A simple model for the variability of R with season and with mean <span class="hlt">ice</span> thickness gives results in reasonable agreement with observations. They show that although there is a large seasonal variability due to snow load, there is a stable period from November to April when the variability is chiefly dependent on the mean <span class="hlt">ice</span> thickness alone. Thus, in principle, R can be mapped over the Arctic Ocean as a basis for interpreting survey data. Better field data are needed on the seasonal and spatial variability of three key</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRC..11211013D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRC..11211013D"><span>Influence of sea <span class="hlt">ice</span> cover and icebergs on circulation and water <span class="hlt">mass</span> formation in a numerical circulation model of the Ross Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dinniman, Michael S.; Klinck, John M.; Smith, Walker O.</p> <p>2007-11-01</p> <p>Satellite imagery shows that there was substantial variability in the sea <span class="hlt">ice</span> extent in the Ross Sea during 2001-2003. Much of this variability is thought to be due to several large icebergs that moved through the area during that period. The effects of these changes in sea <span class="hlt">ice</span> on circulation and water <span class="hlt">mass</span> distributions are investigated with a numerical general circulation model. It would be difficult to simulate the highly variable sea <span class="hlt">ice</span> from 2001 to 2003 with a dynamic sea <span class="hlt">ice</span> model since much of the variability was due to the floating icebergs. Here, sea <span class="hlt">ice</span> concentration is specified from satellite observations. To examine the effects of changes in sea <span class="hlt">ice</span> due to iceberg C-19, simulations were performed using either climatological <span class="hlt">ice</span> concentrations or the observed <span class="hlt">ice</span> for that period. The heat balance around the Ross Sea Polynya (RSP) shows that the dominant term in the surface heat budget is the net exchange with the atmosphere, but advection of oceanic warm water is also important. The area average annual basal melt rate beneath the Ross <span class="hlt">Ice</span> Shelf is reduced by 12% in the observed sea <span class="hlt">ice</span> simulation. The observed sea <span class="hlt">ice</span> simulation also creates more High-Salinity Shelf Water. Another simulation was performed with observed sea <span class="hlt">ice</span> and a fixed iceberg representing B-15A. There is reduced advection of warm surface water during summer from the RSP into McMurdo Sound due to B-15A, but a much stronger reduction is due to the late opening of the RSP in early 2003 because of C-19.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA123762','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA123762"><span>The Growth, Structure, and Properties of Sea <span class="hlt">Ice</span>,</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1982-11-01</p> <p>First, the natural range of temperatures at which sea <span class="hlt">ice</span> exists is just a few degrees off its melting point. In fact, sea <span class="hlt">ice</span> normally is only...surface of lakes and seas. If <span class="hlt">ice</span> sank into its melt, as do most solids, there would be a tendency for natural water bodies to freeze completely to...I I I -c 1 I II I I 02 b . Figure 1. Structure of <span class="hlt">ice</span> I. The fact that ordinary <span class="hlt">ice</span> is such an open, low <span class="hlt">density</span> solid also suggests that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1989PhDT.......144H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1989PhDT.......144H"><span>Monte Carlo Study of Melting of a Model Bulk <span class="hlt">Ice</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Kyu-Kwang</p> <p></p> <p>The methods of NVT (constant number, volume and temperature) and NPT (constant number, pressure and temperature) Monte Carlo computer simulations are used to examine the melting of a periodic hexagonal <span class="hlt">ice</span> (<span class="hlt">ice</span> Ih) sample with a unit cell of 192 (rigid) water molecules interacting via the revised central force potentials of Stillinger and Rahman (RSL2). In NVT Monte Carlo simulation of P-T plot for a constant <span class="hlt">density</span> (0.904g/cm^3) is used to locate onset of the liquid-solid coexistence region (where the slope of the pressure changes sign) and estimate the (constant <span class="hlt">density</span>) melting point. The slope reversal is a natural consequence of the constant <span class="hlt">density</span> condition for substances which expand upon freezing and it is pointed out that this analysis is extremely useful for substances such as water. In this study, a sign reversal of the pressure slope is observed near 280 K, indicating that the RSL2 potentials reproduce the freezing expansion expected for water and support a bulk <span class="hlt">ice</span> Ih system which melts <280 K. The internal energy, specific heat, and two dimensional structure factors for the constant <span class="hlt">density</span> H_2O system are also examined at a range of temperatures between 100 and 370 K and support the P-T analysis for location of the melting point. This P-T analysis might likewise be useful for determining a (constant <span class="hlt">density</span>) freezing point, or, with multiple simulations at appropriate <span class="hlt">densities</span>, the triple point. For NPT Monte Carlo simulations preliminary results are presented. In this study the <span class="hlt">density</span>, enthalpy, specific heat, and structure factor dependences on temperature are monitored during a sequential heating of the system from 100 to 370 K at a constant pressure (1 atm.). A jump in <span class="hlt">density</span> upon melting is observed and indicates that the RSL2 potentials reproduce the melting contraction of <span class="hlt">ice</span>. From the dependences of monitored physical properties on temperature an upper bound on the melting temperature is estimated. In this study we made the first</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA601787','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA601787"><span><span class="hlt">Mass</span> Balance of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-09-30</p> <p>model of MY <span class="hlt">ice</span> circulation, which is shown in Figure 1. In this model , we consider the Beaufort Sea to consist of four zones defined by mean drift...Arctic Regional Climate Model Simulation Project 3 International Arctic Buoy Program 4 Sea <span class="hlt">ice</span> Experiment - Dynamic Nature of the Arctic 5Cold...2 Table 2: Datasets compiled to date Geophysical data type Source Time period acquired Buoy tracks IABP 12 hrly position data 1978-2012 <span class="hlt">Ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1013710','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1013710"><span><span class="hlt">Mass</span> Balance of Multiyear Sea <span class="hlt">Ice</span> in the Southern Beaufort Sea</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-09-30</p> <p>1) Determination of the net growth and melt of multiyear (MY) sea <span class="hlt">ice</span> during its transit through the southern Beaufort Sea 2) Identification of...which we refer to as the FGIV dataset. Analysis of melt processes from <span class="hlt">ice</span> core and IMB data (Eicken) Through stratigraphic analysis of sea <span class="hlt">ice</span>...samples that are brought back to shore were melted and used to determine profiles of salinity and stable isotope ratios. These data allow us to identify</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GMD....11.1257N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GMD....11.1257N"><span>Intercomparison of Antarctic <span class="hlt">ice</span>-shelf, ocean, and sea-<span class="hlt">ice</span> interactions simulated by MetROMS-iceshelf and FESOM 1.4</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naughten, Kaitlin A.; Meissner, Katrin J.; Galton-Fenzi, Benjamin K.; England, Matthew H.; Timmermann, Ralph; Hellmer, Hartmut H.; Hattermann, Tore; Debernard, Jens B.</p> <p>2018-04-01</p> <p>An increasing number of Southern Ocean models now include Antarctic <span class="hlt">ice</span>-shelf cavities, and simulate thermodynamics at the <span class="hlt">ice</span>-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as <span class="hlt">ice</span> shelves interact directly with the ocean and indirectly with sea <span class="hlt">ice</span>. Here, we present the first model intercomparison and evaluation of present-day ocean/sea-<span class="hlt">ice/ice</span>-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community <span class="hlt">Ice</span> CodE) and the global model FESOM (Finite Element Sea-<span class="hlt">ice</span> Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated <span class="hlt">ice</span>-shelf basal melting and sub-<span class="hlt">ice</span>-shelf circulation, as well as sea-<span class="hlt">ice</span> properties and Southern Ocean water <span class="hlt">mass</span> characteristics as they influence the sub-<span class="hlt">ice</span>-shelf processes. Despite their differing numerical methods, the two models produce broadly similar results and share similar biases in many cases. Both models reproduce many key features of observations but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity <span class="hlt">ice</span> shelves of the Amundsen and Bellingshausen seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some <span class="hlt">ice</span>-shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water <span class="hlt">mass</span> erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinate leading to more erosion than FESOM's z coordinate. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small <span class="hlt">ice</span> shelves, through a combination of stronger circulation and small-scale intrusions of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14749827','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14749827"><span>Enhanced <span class="hlt">ice</span> sheet growth in Eurasia owing to adjacent <span class="hlt">ice</span>-dammed lakes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krinner, G; Mangerud, J; Jakobsson, M; Crucifix, M; Ritz, C; Svendsen, J I</p> <p>2004-01-29</p> <p>Large proglacial lakes cool regional summer climate because of their large heat capacity, and have been shown to modify precipitation through mesoscale atmospheric feedbacks, as in the case of Lake Agassiz. Several large <span class="hlt">ice</span>-dammed lakes, with a combined area twice that of the Caspian Sea, were formed in northern Eurasia about 90,000 years ago, during the last glacial period when an <span class="hlt">ice</span> sheet centred over the Barents and Kara seas blocked the large northbound Russian rivers. Here we present high-resolution simulations with an atmospheric general circulation model that explicitly simulates the surface <span class="hlt">mass</span> balance of the <span class="hlt">ice</span> sheet. We show that the main influence of the Eurasian proglacial lakes was a significant reduction of <span class="hlt">ice</span> sheet melting at the southern margin of the Barents-Kara <span class="hlt">ice</span> sheet through strong regional summer cooling over large parts of Russia. In our simulations, the summer melt reduction clearly outweighs lake-induced decreases in moisture and hence snowfall, such as has been reported earlier for Lake Agassiz. We conclude that the summer cooling mechanism from proglacial lakes accelerated <span class="hlt">ice</span> sheet growth and delayed <span class="hlt">ice</span> sheet decay in Eurasia and probably also in North America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SPIE10526E..0VP','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SPIE10526E..0VP"><span>Measuring and engineering the atomic <span class="hlt">mass</span> <span class="hlt">density</span> wave of a Gaussian <span class="hlt">mass</span>-polariton pulse in optical fibers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Partanen, Mikko; Tulkki, Jukka</p> <p>2018-02-01</p> <p>Conventional theories of electromagnetic waves in a medium assume that only the energy of the field propagates inside the medium. Consequently, they neglect the transport of <span class="hlt">mass</span> <span class="hlt">density</span> by the medium atoms. We have recently presented foundations of a covariant theory of light propagation in a nondispersive medium by considering a light wave simultaneously with the dynamics of the medium atoms driven by optoelastic forces [Phys. Rev. A 95, 063850 (2017)]. In particular, we have shown that the <span class="hlt">mass</span> is transferred by an atomic <span class="hlt">mass</span> <span class="hlt">density</span> wave (MDW), which gives rise to <span class="hlt">mass</span>-polariton (MP) quasiparticles, i.e., covariant coupled states of the field and matter having a nonzero rest <span class="hlt">mass</span>. Another key observation of the <span class="hlt">mass</span>-polariton theory of light is that, in common semiconductors, most of the momentum of light is transferred by moving atoms, e.g., 92% in the case of silicon. In this work, we generalize the MP theory of light for dispersive media and consider experimental measurement of the <span class="hlt">mass</span> transferred by the MDW atoms when an intense light pulse propagates in a silicon fiber. In particular, we consider optimal intensity and time dependence of a Gaussian pulse and account for the breakdown threshold irradiance of the material. The optical shock wave property of the MDW, which propagates with the velocity of light instead of the velocity of sound, prompts for engineering of novel device concepts like very high frequency mechanical oscillators not limited by the acoustic cutoff frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRD..11811136S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRD..11811136S"><span>The microphysical properties of <span class="hlt">ice</span> fog measured in urban environments of Interior Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmitt, Carl G.; Stuefer, Martin; Heymsfield, Andrew J.; Kim, Chang Ki</p> <p>2013-10-01</p> <p>microphysical properties of <span class="hlt">ice</span> fog were measured at two sites during a small field campaign in January and February of 2012 in Interior Alaska. The National Center for Atmospheric Research Video <span class="hlt">Ice</span> Particle Sampler probe and Formvar (polyvinyl formal)-coated microscope slides were used to sample airborne <span class="hlt">ice</span> particles at two polluted sites in the Fairbanks region. Both sites were significantly influenced by anthropogenic emission and additional water vapor from nearby open water power plant cooling ponds. Measurements show that <span class="hlt">ice</span> fog particles were generally droxtal shaped (faceted, quasi-spherical) for sub-10 µm particles, while plate-shaped crystals were the most frequently observed particles between 10 and 50 µm. A visibility cutoff of 3 km was used to separate <span class="hlt">ice</span> fog events from other observations which were significantly influenced by larger (50-150 µm) diamond dust particles. The purpose of this study is to more realistically characterize <span class="hlt">ice</span> fog microphysical properties in order to facilitate better model predictions of the onset of <span class="hlt">ice</span> fog in polluted environments. Parameterizations for <span class="hlt">mass</span> and projected area are developed and used to estimate particle terminal velocity. Dimensional characteristics are based on particle geometry and indicated that <span class="hlt">ice</span> fog particles have significantly lower <span class="hlt">densities</span> than water droplets as well as reduced cross-sectional areas, the net result being that terminal velocities are estimated to be less than half the value of those calculated for water droplets. Particle size distributions are characterized using gamma functions and have a shape factor (μ) of between -0.5 and -1.0 for polluted <span class="hlt">ice</span> fog conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ChJOL..33..458Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ChJOL..33..458Z"><span>Influences of sea <span class="hlt">ice</span> on eastern Bering Sea phytoplankton</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Qianqian; Wang, Peng; Chen, Changping; Liang, Junrong; Li, Bingqian; Gao, Yahui</p> <p>2015-03-01</p> <p>The influence of sea <span class="hlt">ice</span> on the species composition and cell <span class="hlt">density</span> of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica (Grunow in Van Heurck) Hasle, Fragilariopsis cylindrus (Grunow) Krieger, F. oceanica (Cleve) Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskiöeldii Cleve, and T. rotula Meunier. Phytoplankton cell <span class="hlt">densities</span> varied from 0.08×104 to 428.8×104 cells/L, with an average of 30.3×104 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by <span class="hlt">ice</span>-forming conditions: open water, <span class="hlt">ice</span> edge, and sea <span class="hlt">ice</span> assemblages. In spring, when the sea <span class="hlt">ice</span> melts, the phytoplankton dispersed from the sea <span class="hlt">ice</span> to the <span class="hlt">ice</span> edge and even into open waters. Thus, these phytoplankton in the sea <span class="hlt">ice</span> may serve as a "seed bank" for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70074767','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70074767"><span>Climatic impact of glacial cycle polar motion: Coupled oscillations of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> and rotation pole position</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bills, Bruce G.; James, Thomas S.; Mengel, John G.</p> <p>1999-01-01</p> <p>Precessional motion of Earth's rotation axis relative to its orbit is a well-known source of long-period climatic variation. It is less well appreciated that growth and decay of polar <span class="hlt">ice</span> sheets perturb the symmetry of the global <span class="hlt">mass</span> distribution enough that the geographic location of the rotation axis will change by at least 15 km and possibly as much as 100 km during a single glacial cycle. This motion of the pole will change the seasonal and latitudinal pattern of temperatures. We present calculations, based on a diurnal average energy balance, which compare the summer and winter temperature anomalies due to a 1° decrease in obliquity with those due to a 1° motion of the rotation pole toward Hudson Bay. Both effects result in peak temperature perturbations of about 1° Celsius. The obliquity change primarily influences the amplitude of the seasonal cycle, while the polar motion primarily changes the annual mean temperatures. The polar motion induced temperature anomaly is such that it will act as a powerful negative feedback on <span class="hlt">ice</span> sheet growth. We also explore the evolution of the coupled system composed of <span class="hlt">ice</span> sheet <span class="hlt">mass</span> and pole position. Oscillatory solutions result from the conflicting constraints of rotational and thermal stability. A positive <span class="hlt">mass</span> anomaly on an otherwise featureless Earth is in rotational equilibrium only at the poles or the equator. The two polar equilibria are rotationally unstable, and the equatorial equilibrium, though rotationally stable, is thermally unstable. We find that with a plausible choice for the strength of coupling between the thermal and rotational systems, relatively modest external forcing can produce significant response at periods of 104–106 years, but it strongly attenuates polar motion at longer periods. We suggest that these coupled oscillations may contribute to the observed dominance of 100 kyr glacial cycles since the mid-Pleistocene and will tend to stabilize geographic patterns that are suitable to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017QSRv..163..114D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017QSRv..163..114D"><span>Phased occupation and retreat of the last British-Irish <span class="hlt">Ice</span> Sheet in the southern North Sea; geomorphic and seismostratigraphic evidence of a dynamic <span class="hlt">ice</span> lobe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dove, Dayton; Evans, David J. A.; Lee, Jonathan R.; Roberts, David H.; Tappin, David R.; Mellett, Claire L.; Long, David; Callard, S. Louise</p> <p>2017-05-01</p> <p>Along the terrestrial margin of the southern North Sea, previous studies of the MIS 2 glaciation impacting eastern Britain have played a significant role in the development of principles relating to <span class="hlt">ice</span> sheet dynamics (e.g. deformable beds), and the practice of reconstructing the style, timing, and spatial configuration of palaeo-<span class="hlt">ice</span> sheets. These detailed terrestrially-based findings have however relied on observations made from only the outer edges of the former <span class="hlt">ice</span> <span class="hlt">mass</span>, as the North Sea Lobe (NSL) of the British-Irish <span class="hlt">Ice</span> Sheet (BIIS) occupied an area that is now almost entirely submarine (c.21-15 ka). Compounded by the fact that marine-acquired data have been primarily of insufficient quality and <span class="hlt">density</span>, the configuration and behaviour of the last BIIS in the southern North Sea remains surprisingly poorly constrained. This paper presents analysis of a new, integrated set of extensive seabed geomorphological and seismo-stratigraphic observations that both advances the principles developed previously onshore (e.g. multiple advance and retreat cycles), and provides a more detailed and accurate reconstruction of the BIIS at its southern-most extent in the North Sea. A new bathymetry compilation of the region reveals a series of broad sedimentary wedges and associated moraines that represent several terminal positions of the NSL. These former still-stand <span class="hlt">ice</span> margins (1-4) are also found to relate to newly-identified architectural patterns (shallow stacked sedimentary wedges) in the region's seismic stratigraphy (previously mapped singularly as the Bolders Bank Formation). With ground-truthing constraint provided by sediment cores, these wedges are interpreted as sub-marginal till wedges, formed by complex subglacial accretionary processes that resulted in till thickening towards the former <span class="hlt">ice</span>-sheet margins. The newly sub-divided shallow seismic stratigraphy (at least five units) also provides an indication of the relative event chronology of the NSL. While there</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.G13B1098S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G13B1098S"><span>An integrated approach for estimating global glacio isostatic adjustment, land <span class="hlt">ice</span>, hydrology and ocean <span class="hlt">mass</span> trends within a complete coupled Earth system framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schumacher, M.; Bamber, J. L.; Martin, A.</p> <p>2016-12-01</p> <p>Future sea level rise (SLR) is one of the most serious consequences of climate change. Therefore, understanding the drivers of past sea level change is crucial for improving predictions. SLR integrates many Earth system components including oceans, land <span class="hlt">ice</span>, terrestrial water storage, as well as solid Earth effects. Traditionally, each component have been tackled separately, which has often lead to inconsistencies between discipline-specific estimates of each part of the sea level budget. To address these issues, the European Research Council has funded a five year project aimed at producing a physically-based, data-driven solution for the complete coupled land-ocean-solid Earth system that is consistent with the full suite of observations, prior knowledge and fundamental geophysical constraints. The project is called "Global<span class="hlt">Mass</span>" and based at University of Bristol. Observed <span class="hlt">mass</span> movement from the GRACE mission plus vertical land motion from a global network of permanent GPS stations will be utilized in a data-driven approach to estimate glacial isostatic adjustment (GIA) without introducing any assumptions about the Earth structure or <span class="hlt">ice</span> loading history. A Bayesian Hierarchical Model (BHM) will be used as the framework to combine the satellite and in-situ observations alongside prior information that incorporates the physics of the coupled system such as conservation of <span class="hlt">mass</span> and characteristic length scales of different processes in both space and time. The BHM is used to implement a simultaneous solution at a global scale. It will produce a consistent partitioning of the integrated SLR signal into its steric (thermal) and barystatic (<span class="hlt">mass</span>) component for the satellite era. The latter component is induced by hydrological <span class="hlt">mass</span> trends and melting of land <span class="hlt">ice</span>. The BHM was developed and tested on Antarctica, where it has been used to separate surface, <span class="hlt">ice</span> dynamic and GIA signals simultaneously. We illustrate the approach and concepts with examples from this test case</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860056170&hterms=waco&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dwaco','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860056170&hterms=waco&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dwaco"><span>Dust <span class="hlt">density</span> and <span class="hlt">mass</span> distribution near comet Halley from Giotto observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcdonnell, J. A. M.; Alexander, W. M.; Burton, W. M.; Bussoletti, E.; Clark, D. H.; Grard, J. L.; Gruen, E.; Hanner, M. S.; Sekanina, Z.; Hughes, D. W.</p> <p>1986-01-01</p> <p>The <span class="hlt">density</span> and the <span class="hlt">mass</span> spectrum of the dust near comet Halley have been measured by the Giotto space probe's dust impact detection system. The dust spectrum obtained at 291,000 km from the comet nucleus show depletion in small and intermediate <span class="hlt">masses</span>; at about 600 km from the nucleus, however, the dust activity rises and the spectrum is dominated by larger <span class="hlt">masses</span>. Most of the <span class="hlt">mass</span> striking Giotto is noted to reside in the few large particles penetrating the dust shield. Momentum balances and energy considerations applied to an observed deceleration suggest that a large <span class="hlt">mass</span> of the spacecraft was detached by an impact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170003145','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170003145"><span>Antarctic Sea-<span class="hlt">Ice</span> Freeboard and Estimated Thickness from NASA's ICESat and <span class="hlt">Ice</span>Bridge Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yi, Donghui; Kurtz, Nathan; Harbeck, Jeremy; Manizade, Serdar; Hofton, Michelle; Cornejo, Helen G.; Zwally, H. Jay; Robbins, John</p> <p>2016-01-01</p> <p>ICESat completed 18 observational campaigns during its lifetime from 2003 to 2009. Data from all of the 18 campaign periods are used in this study. Most of the operational periods were between 34 and 38 days long. Because of laser failure and orbit transition from 8-day to 91-day orbit, there were four periods lasting 57, 16, 23, and 12 days. <span class="hlt">Ice</span>Bridge data from 2009, 2010, and 2011 are used in this study. Since 2009, there are 19 Airborne Topographic Mapper (ATM) campaigns, and eight Land, Vegetation, and <span class="hlt">Ice</span> Sensor (LVIS) campaigns over the Antarctic sea <span class="hlt">ice</span>. Freeboard heights are derived from ICESat, ATM and LVIS elevation and waveform data. With nominal <span class="hlt">densities</span> of snow, water, and sea <span class="hlt">ice</span>, combined with snow depth data from AMSR-E/AMSR2 passive microwave observation over the southern ocean, sea-<span class="hlt">ice</span> thickness is derived from the freeboard. Combined with AMSR-E/AMSR2 <span class="hlt">ice</span> concentration, sea-<span class="hlt">ice</span> area and volume are also calculated. During the 2003-2009 period, sea-<span class="hlt">ice</span> freeboard and thickness distributions show clear seasonal variations that reflect the yearly cycle of the growth and decay of the Antarctic pack <span class="hlt">ice</span>. We found no significant trend of thickness or area for the Antarctic sea <span class="hlt">ice</span> during the ICESat period. <span class="hlt">Ice</span>Bridge sea <span class="hlt">ice</span> freeboard and thickness data from 2009 to 2011 over the Weddell Sea and Amundsen and Bellingshausen Seas are compared with the ICESat results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950040584&hterms=Mass+standards&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DMass%2Bstandards','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950040584&hterms=Mass+standards&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DMass%2Bstandards"><span>Amplitude of primeval fluctuations from cosmological <span class="hlt">mass</span> <span class="hlt">density</span> reconstructions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Seljak, Uros; Bertschinger, Edmund</p> <p>1994-01-01</p> <p>We use the POTENT reconstruction of the <span class="hlt">mass</span> <span class="hlt">density</span> field in the nearby universe to estimate the amplitude of the <span class="hlt">density</span> fluctuation power spectrum for various cosmological models. We find that sigma(sub 8) Omega(sub m sup 0.6) = 1.3(sub -0.3 sup +0.4), almost independently of the power spectrum. This value agrees well with the Cosmic Background Explorer (COBE) normalization for the standard cold dark matter model, while alternative models predict an excessive amplitude compared with COBE. Flat, low Omega(sub m) models and tilted models with spectral index n less than 0.8 are particularly discordant.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5642703','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5642703"><span>Katabatic winds diminish precipitation contribution to the Antarctic <span class="hlt">ice</span> <span class="hlt">mass</span> balance</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Grazioli, Jacopo; Madeleine, Jean-Baptiste; Gallée, Hubert; Forbes, Richard M.; Genthon, Christophe; Krinner, Gerhard; Berne, Alexis</p> <p>2017-01-01</p> <p>Snowfall in Antarctica is a key term of the <span class="hlt">ice</span> sheet <span class="hlt">mass</span> budget that influences the sea level at global scale. Over the continental margins, persistent katabatic winds blow all year long and supply the lower troposphere with unsaturated air. We show that this dry air leads to significant low-level sublimation of snowfall. We found using unprecedented data collected over 1 year on the coast of Adélie Land and simulations from different atmospheric models that low-level sublimation accounts for a 17% reduction of total snowfall over the continent and up to 35% on the margins of East Antarctica, significantly affecting satellite-based estimations close to the ground. Our findings suggest that, as climate warming progresses, this process will be enhanced and will limit expected precipitation increases at the ground level. PMID:28973875</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22218229-low-temperature-growth-ultra-high-mass-density-carbon-nanotube-forests-conductive-supports','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22218229-low-temperature-growth-ultra-high-mass-density-carbon-nanotube-forests-conductive-supports"><span>Low temperature growth of ultra-high <span class="hlt">mass</span> <span class="hlt">density</span> carbon nanotube forests on conductive supports</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Sugime, Hisashi; Esconjauregui, Santiago; Yang, Junwei</p> <p>2013-08-12</p> <p>We grow ultra-high <span class="hlt">mass</span> <span class="hlt">density</span> carbon nanotube forests at 450 °C on Ti-coated Cu supports using Co-Mo co-catalyst. X-ray photoelectron spectroscopy shows Mo strongly interacts with Ti and Co, suppressing both aggregation and lifting off of Co particles and, thus, promoting the root growth mechanism. The forests average a height of 0.38 μm and a <span class="hlt">mass</span> <span class="hlt">density</span> of 1.6 g cm{sup −3}. This <span class="hlt">mass</span> <span class="hlt">density</span> is the highest reported so far, even at higher temperatures or on insulators. The forests and Cu supports show ohmic conductivity (lowest resistance ∼22 kΩ), suggesting Co-Mo is useful for applications requiring forest growth onmore » conductors.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP52A..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP52A..04A"><span>How and when to terminate the Pleistocene <span class="hlt">ice</span> ages?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abe-Ouchi, A.; Saito, F.; Kawamura, K.; Takahashi, K.; Raymo, M. E.; Okuno, J.; Blatter, H.</p> <p>2015-12-01</p> <p>Climate change with wax and wane of large Northern Hemisphere <span class="hlt">ice</span> sheet occurred in the past 800 thousand years characterized by 100 thousand year cycle with a large amplitude of sawtooth pattern, following a transition from a period of 40 thousand years cycle with small amplitude of <span class="hlt">ice</span> sheet change at about 1 million years ago. Although the importance of insolation as the ultimate driver is now appreciated, the mechanism what determines timing and strength of terminations are far from clearly understood. Here we show, using comprehensive climate and <span class="hlt">ice</span>-sheet models, that insolation and internal feedbacks between the climate, the <span class="hlt">ice</span> sheets and the lithosphere-asthenosphere system explain the 100,000-year periodicity. The responses of equilibrium states of <span class="hlt">ice</span> sheets to summer insolation show hysteresis, with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles. The hysteresis loop of the North American <span class="hlt">ice</span> sheet is such that after inception of the <span class="hlt">ice</span> sheet, its <span class="hlt">mass</span> balance remains mostly positive through several precession cycles, whose amplitudes decrease towards an eccentricity minimum. The larger the <span class="hlt">ice</span> sheet grows and extends towards lower latitudes, the smaller is the insolation required to make the <span class="hlt">mass</span> balance negative. Therefore, once a large <span class="hlt">ice</span> sheet is established, a moderate increase in insolation is sufficient to trigger a negative <span class="hlt">mass</span> balance, leading to an almost complete retreat of the <span class="hlt">ice</span> sheet within several thousand years. We discuss further the mechanism which determine the timing of <span class="hlt">ice</span> age terminations by examining the role of astronomical forcing and change of atmospheric carbon dioxide contents through sensitivity experiments and comparison of several <span class="hlt">ice</span> age cycles with different settings of astronomical forcings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009QSRv...28.3101G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009QSRv...28.3101G"><span>Reconstructing the last Irish <span class="hlt">Ice</span> Sheet 2: a geomorphologically-driven model of <span class="hlt">ice</span> sheet growth, retreat and dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greenwood, Sarah L.; Clark, Chris D.</p> <p>2009-12-01</p> <p>The <span class="hlt">ice</span> sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and <span class="hlt">ice</span>-marginal dynamics and chronologies, with less attention paid to an <span class="hlt">ice</span> sheet wide view of the first order properties of the <span class="hlt">ice</span> sheet: centres of <span class="hlt">mass</span>, <span class="hlt">ice</span> divide structure, <span class="hlt">ice</span> flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an <span class="hlt">ice</span> sheet reconstruction yielding these fundamental <span class="hlt">ice</span> sheet properties. We present a seven stage model of <span class="hlt">ice</span> sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of <span class="hlt">ice</span> from Scotland likely coalesced with local <span class="hlt">ice</span> caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish <span class="hlt">Ice</span> Sheet was then established during <span class="hlt">ice</span> sheet growth, with a branching <span class="hlt">ice</span> divide structure whose main axis migrated up to 140 km from the west coast towards the east. <span class="hlt">Ice</span> stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. <span class="hlt">Ice</span> cover is reconstructed as extending to the continental shelf break. The Irish <span class="hlt">Ice</span> Sheet became autonomous (i.e. separate from the British <span class="hlt">Ice</span> Sheet) during deglaciation and fragmented into multiple <span class="hlt">ice</span> <span class="hlt">masses</span>, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the <span class="hlt">ice</span> sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the <span class="hlt">ice</span> stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70027302','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70027302"><span>DEM, tide and velocity over sulzberger <span class="hlt">ice</span> shelf, West Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Baek, S.; Shum, C.K.; Lee, H.; Yi, Y.; Kwoun, Oh-Ig; Lu, Z.; Braun, Andreas</p> <p>2005-01-01</p> <p>Arctic and Antarctic <span class="hlt">ice</span> sheets preserve more than 77% of the global fresh water and could raise global sea level by several meters if completely melted. Ocean tides near and under <span class="hlt">ice</span> shelves shifts the grounding line position significantly and are one of current limitations to study glacier dynamics and <span class="hlt">mass</span> balance. The Sulzberger <span class="hlt">ice</span> shelf is an area of <span class="hlt">ice</span> <span class="hlt">mass</span> flux change in West Antarctica and has not yet been well studied. In this study, we use repeat-pass synthetic aperture radar (SAR) interferometry data from the ERS-1 and ERS-2 tandem missions for generation of a high-resolution (60-m) Digital Elevation Model (DEM) including tidal deformation detection and <span class="hlt">ice</span> stream velocity of the Sulzberger <span class="hlt">Ice</span> Shelf. Other satellite data such as laser altimeter measurements with fine foot-prints (70-m) from NASA's ICESat are used for validation and analyses. The resulting DEM has an accuracy of-0.57??5.88 m and is demonstrated to be useful for grounding line detection and <span class="hlt">ice</span> <span class="hlt">mass</span> balance studies. The deformation observed by InSAR is found to be primarily due to ocean tides and atmospheric pressure. The 2-D <span class="hlt">ice</span> stream velocities computed agree qualitatively with previous methods on part of the <span class="hlt">Ice</span> Shelf from passive microwave remote-sensing data (i.e., LANDSAT). ?? 2005 IEEE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28518108','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28518108"><span>Identification of Plant <span class="hlt">Ice</span>-binding Proteins Through Assessment of <span class="hlt">Ice</span>-recrystallization Inhibition and Isolation Using <span class="hlt">Ice</span>-affinity Purification.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bredow, Melissa; Tomalty, Heather E; Walker, Virginia K</p> <p>2017-05-05</p> <p><span class="hlt">Ice</span>-binding proteins (IBPs) belong to a family of stress-induced proteins that are synthesized by certain organisms exposed to subzero temperatures. In plants, freeze damage occurs when extracellular <span class="hlt">ice</span> crystals grow, resulting in the rupture of plasma membranes and possible cell death. Adsorption of IBPs to <span class="hlt">ice</span> crystals restricts further growth by a process known as <span class="hlt">ice</span>-recrystallization inhibition (IRI), thereby reducing cellular damage. IBPs also demonstrate the ability to depress the freezing point of a solution below the equilibrium melting point, a property known as thermal hysteresis (TH) activity. These protective properties have raised interest in the identification of novel IBPs due to their potential use in industrial, medical and agricultural applications. This paper describes the identification of plant IBPs through 1) the induction and extraction of IBPs in plant tissue, 2) the screening of extracts for IRI activity, and 3) the isolation and purification of IBPs. Following the induction of IBPs by low temperature exposure, extracts are tested for IRI activity using a 'splat assay', which allows the observation of <span class="hlt">ice</span> crystal growth using a standard light microscope. This assay requires a low protein concentration and generates results that are quickly obtained and easily interpreted, providing an initial screen for <span class="hlt">ice</span> binding activity. IBPs can then be isolated from contaminating proteins by utilizing the property of IBPs to adsorb to <span class="hlt">ice</span>, through a technique called '<span class="hlt">ice</span>-affinity purification'. Using cell lysates collected from plant extracts, an <span class="hlt">ice</span> hemisphere can be slowly grown on a brass probe. This incorporates IBPs into the crystalline structure of the polycrystalline <span class="hlt">ice</span>. Requiring no a priori biochemical or structural knowledge of the IBP, this method allows for recovery of active protein. <span class="hlt">Ice</span>-purified protein fractions can be used for downstream applications including the identification of peptide sequences by <span class="hlt">mass</span> spectrometry and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028080','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028080"><span>Satellite-derived, melt-season surface temperature of the Greenland <span class="hlt">Ice</span> Sheet (2000-2005) and its relationship to <span class="hlt">mass</span> balance</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hall, D.K.; Williams, R.S.; Casey, K.A.; DiGirolamo, N.E.; Wan, Z.</p> <p>2006-01-01</p> <p>Mean, clear-sky surface temperature of the Greenland <span class="hlt">Ice</span> Sheet was measured for each melt season from 2000 to 2005 using Moderate-Resolution Imaging Spectroradiometer (MODIS)–derived land-surface temperature (LST) data-product maps. During the period of most-active melt, the mean, clear-sky surface temperature of the <span class="hlt">ice</span> sheet was highest in 2002 (−8.29 ± 5.29°C) and 2005 (−8.29 ± 5.43°C), compared to a 6-year mean of −9.04 ± 5.59°C, in agreement with recent work by other investigators showing unusually extensive melt in 2002 and 2005. Surface-temperature variability shows a correspondence with the dry-snow facies of the <span class="hlt">ice</span> sheet; a reduction in area of the dry-snow facies would indicate a more-negative <span class="hlt">mass</span> balance. Surface-temperature variability generally increased during the study period and is most pronounced in the 2005 melt season; this is consistent with surface instability caused by air-temperature fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890018778','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890018778"><span>Analysis of sea <span class="hlt">ice</span> dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, J.</p> <p>1988-01-01</p> <p>The ongoing work has established the basis for using multiyear sea <span class="hlt">ice</span> concentrations from SMMR passive microwave for studies of largescale advection and convergence/divergence of the Arctic sea <span class="hlt">ice</span> pack. Comparisons were made with numerical model simulations and buoy data showing qualitative agreement on daily to interannual time scales. Analysis of the 7-year SMMR data set shows significant interannual variations in the total area of multiyear <span class="hlt">ice</span>. The scientific objective is to investigate the dynamics, <span class="hlt">mass</span> balance, and interannual variability of the Arctic sea <span class="hlt">ice</span> pack. The research emphasizes the direct application of sea <span class="hlt">ice</span> parameters derived from passive microwave data (SMMR and SSMI) and collaborative studies using a sea <span class="hlt">ice</span> dynamics model. The possible causes of observed interannual variations in the multiyear <span class="hlt">ice</span> area are being examined. The relative effects of variations in the large scale advection and convergence/divergence within the <span class="hlt">ice</span> pack on a regional and seasonal basis are investigated. The effects of anomolous atmospheric forcings are being examined, including the long-lived effects of synoptic events and monthly variations in the mean geostrophic winds. Estimates to be made will include the amount of new <span class="hlt">ice</span> production within the <span class="hlt">ice</span> pack during winter and the amount of <span class="hlt">ice</span> exported from the pack.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...571A..95F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...571A..95F"><span>On the probability distribution function of the <span class="hlt">mass</span> surface <span class="hlt">density</span> of molecular clouds. II.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischera, Jörg</p> <p>2014-11-01</p> <p>The probability distribution function (PDF) of the <span class="hlt">mass</span> surface <span class="hlt">density</span> of molecular clouds provides essential information about the structure of molecular cloud gas and condensed structures out of which stars may form. In general, the PDF shows two basic components: a broad distribution around the maximum with resemblance to a log-normal function, and a tail at high <span class="hlt">mass</span> surface <span class="hlt">densities</span> attributed to turbulence and self-gravity. In a previous paper, the PDF of condensed structures has been analyzed and an analytical formula presented based on a truncated radial <span class="hlt">density</span> profile, ρ(r) = ρc/ (1 + (r/r0)2)n/ 2 with central <span class="hlt">density</span> ρc and inner radius r0, widely used in astrophysics as a generalization of physical <span class="hlt">density</span> profiles. In this paper, the results are applied to analyze the PDF of self-gravitating, isothermal, pressurized, spherical (Bonnor-Ebert spheres) and cylindrical condensed structures with emphasis on the dependence of the PDF on the external pressure pext and on the overpressure q-1 = pc/pext, where pc is the central pressure. Apart from individual clouds, we also consider ensembles of spheres or cylinders, where effects caused by a variation of pressure ratio, a distribution of condensed cores within a turbulent gas, and (in case of cylinders) a distribution of inclination angles on the mean PDF are analyzed. The probability distribution of pressure ratios q-1 is assumed to be given by P(q-1) ∝ q-k1/ (1 + (q0/q)γ)(k1 + k2) /γ, where k1, γ, k2, and q0 are fixed parameters. The PDF of individual spheres with overpressures below ~100 is well represented by the PDF of a sphere with an analytical <span class="hlt">density</span> profile with n = 3. At higher pressure ratios, the PDF at <span class="hlt">mass</span> surface <span class="hlt">densities</span> Σ ≪ Σ(0), where Σ(0) is the central <span class="hlt">mass</span> surface <span class="hlt">density</span>, asymptotically approaches the PDF of a sphere with n = 2. Consequently, the power-law asymptote at <span class="hlt">mass</span> surface <span class="hlt">densities</span> above the peak steepens from Psph(Σ) ∝ Σ-2 to Psph(Σ) ∝ Σ-3. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19624212','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19624212"><span>The phase diagram of water at negative pressures: virtual <span class="hlt">ices</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Conde, M M; Vega, C; Tribello, G A; Slater, B</p> <p>2009-07-21</p> <p>The phase diagram of water at negative pressures as obtained from computer simulations for two models of water, TIP4P/2005 and TIP5P is presented. Several solid structures with lower <span class="hlt">densities</span> than <span class="hlt">ice</span> Ih, so-called virtual <span class="hlt">ices</span>, were considered as possible candidates to occupy the negative pressure region of the phase diagram of water. In particular the empty hydrate structures sI, sII, and sH and another, recently proposed, low-<span class="hlt">density</span> <span class="hlt">ice</span> structure. The relative stabilities of these structures at 0 K was determined using empirical water potentials and <span class="hlt">density</span> functional theory calculations. By performing free energy calculations and Gibbs-Duhem integration the phase diagram of TIP4P/2005 was determined at negative pressures. The empty hydrates sII and sH appear to be the stable solid phases of water at negative pressures. The phase boundary between <span class="hlt">ice</span> Ih and sII clathrate occurs at moderate negative pressures, while at large negative pressures sH becomes the most stable phase. This behavior is in reasonable agreement with what is observed in <span class="hlt">density</span> functional theory calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011MsT.........18M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011MsT.........18M"><span>Quantification of Changes for the Milne <span class="hlt">Ice</span> Shelf, Nunavut, Canada, 1950 -- 2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mortimer, Colleen Adel</p> <p></p> <p>This study presents a comprehensive overview of the current state of the Milne <span class="hlt">Ice</span> Shelf and how it has changed over the last 59 years. The 205 +/-1 km2 <span class="hlt">ice</span> shelf experienced a 28% (82 +/-0.8 km 2) reduction in area between 1950 -- 2009, and a 20% (2.5 +/-0.9km 3 water equivalent (w.e.)) reduction in volume between 1981 -- 2008/2009, suggesting a long-term state of negative <span class="hlt">mass</span> balance. Comparison of mean annual specific <span class="hlt">mass</span> balances (up to -0.34 m w.e. yr-1) with surface <span class="hlt">mass</span> balance measurements for the nearby Ward Hunt <span class="hlt">Ice</span> Shelf suggest that basal melt is a key contributor to total <span class="hlt">ice</span> shelf thinning. The development and expansion of new and existing surface cracks, as well as <span class="hlt">ice</span>-marginal and epishelf lake development, indicate significant <span class="hlt">ice</span> shelf weakening. Over the next few decades it is likely that the Milne <span class="hlt">Ice</span> Shelf will continue to deteriorate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20601297','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20601297"><span>Effects of badminton and <span class="hlt">ice</span> hockey on bone <span class="hlt">mass</span> in young males: a 12-year follow-up.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tervo, Taru; Nordström, Peter; Nordström, Anna</p> <p>2010-09-01</p> <p>The purpose of the present study was to investigate the influence of different types of weight bearing physical activity on bone mineral <span class="hlt">density</span> (BMD, g/cm(2)) and evaluate any residual benefits after the active sports career. Beginning at 17 years of age, BMD was measured 5 times, during 12 years, in 19 badminton players, 48 <span class="hlt">ice</span> hockey players, and 25 controls. During the active career, badminton players gained significantly more BMD compared to <span class="hlt">ice</span> hockey players at all sites: in their femoral neck (mean difference (Delta) 0.06 g/cm(2), p=0.04), humerus (Delta 0.06 g/cm(2), p=0.01), lumbar spine (Delta 0.08 g/cm(2), p=0.01), and their legs (Delta 0.05 g/cm(2), p=0.003), after adjusting for age at baseline, changes in weight, height, and active years. BMD gains in badminton players were higher also compared to in controls at all sites (Delta 0.06-0.17 g/cm(2), p<0.01 for all). Eleven badminton players and 37 <span class="hlt">ice</span> hockey players stopped their active career a mean of 6 years before the final follow-up. Both these groups lost significantly more BMD at the femoral neck and lumbar spine compared to the control group (Delta 0.05-0.12 g/cm(2), p<0.05 for all). At the final follow-up, badminton players had significantly higher BMD of the femoral neck, humerus, lumbar spine, and legs (Delta 0.08-0.20 g/cm(2), p<0.01 for all) than both <span class="hlt">ice</span> hockey players and controls. In summary, the present study may suggest that badminton is a more osteogenic sport compared to <span class="hlt">ice</span> hockey. The BMD benefits from previous training were partially sustained with reduced activity. Copyright 2010 Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC43H1150W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC43H1150W"><span>Geoengineering Marine <span class="hlt">Ice</span> Sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolovick, M.</p> <p>2017-12-01</p> <p><span class="hlt">Mass</span> loss from Greenland and Antarctica is highly sensitive to the presence of warm ocean water that drives melting at the grounding line. Rapid melting near the grounding line causes <span class="hlt">ice</span> shelf thinning, loss of buttressing, flow acceleration, grounding line retreat, and ultimately <span class="hlt">mass</span> loss and sea-level rise. If the grounding line enters a section of overdeepened bed the <span class="hlt">ice</span> sheet may even enter a runaway collapse via the marine <span class="hlt">ice</span> sheet instability. The warm water that triggers this process resides offshore at depth and accesses the grounding line through deep troughs in the continental shelf. In Greenland, warm water transport is further constricted through narrow fjords. Here, I propose blocking warm water transport through these choke points with an artificial sill. Using a simple width- and depth-averaged model of <span class="hlt">ice</span> stream flow coupled to a buoyant-plume model of ocean melting, I find that grounding line retreat and sea level rise can be delayed or reversed for hundreds of years if warm water is prevented from accessing the grounding line at depth. Blocking of warm water from the sub-<span class="hlt">ice</span> cavity causes <span class="hlt">ice</span> shelf thickening, increased buttressing, and grounding line readvance. The increase in buttressing is greatly magnified if the thickened <span class="hlt">ice</span> shelf regrounds on a bathymetric high or on the artificial sill itself. In some experiments for Thwaites Glacier the grounding line is able to recover from a severely retreated state over 100 km behind its present-day position. Such a dramatic recovery demonstrates that it is possible, at least in principle, to stop and reverse an ongoing marine <span class="hlt">ice</span> sheet collapse. If the <span class="hlt">ice</span> shelf regrounds on the artificial sill itself, erosion of the sill beneath the grounded <span class="hlt">ice</span> could reduce the effectiveness of the intervention. However, experiments including sill erosion suggest that even a very weak sill (1 kPa) could delay a collapse for centuries. The scale of the artificial sills in Greenlandic fjords is comparable to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24160528','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24160528"><span>On the accuracy of van der Waals inclusive <span class="hlt">density</span>-functional theory exchange-correlation functionals for <span class="hlt">ice</span> at ambient and high pressures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Santra, Biswajit; Klimes, Jirí; Tkatchenko, Alexandre; Alfè, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias</p> <p>2013-10-21</p> <p><span class="hlt">Density</span>-functional theory (DFT) has been widely used to study water and <span class="hlt">ice</span> for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on <span class="hlt">ice</span> Ih and six proton ordered phases of <span class="hlt">ice</span>. Consistent with our previous study [B. Santra, J. Klimeš, D. Alfè, A. Tkatchenko, B. Slater, A. Michaelides, R. Car, and M. Scheffler, Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure <span class="hlt">ice</span> phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure <span class="hlt">ice</span> phases pose they should be used in future benchmark studies of simulation methods for water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AcMSn..31....1Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AcMSn..31....1Z"><span>Modeling ocean wave propagation under sea <span class="hlt">ice</span> covers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Xin; Shen, Hayley H.; Cheng, Sukun</p> <p>2015-02-01</p> <p>Operational ocean wave models need to work globally, yet current ocean wave models can only treat <span class="hlt">ice</span>-covered regions crudely. The purpose of this paper is to provide a brief overview of <span class="hlt">ice</span> effects on wave propagation and different research methodology used in studying these effects. Based on its proximity to land or sea, sea <span class="hlt">ice</span> can be classified as: landfast <span class="hlt">ice</span> zone, shear zone, and the marginal <span class="hlt">ice</span> zone. All <span class="hlt">ice</span> covers attenuate wave energy. Only long swells can penetrate deep into an <span class="hlt">ice</span> cover. Being closest to open water, wave propagation in the marginal <span class="hlt">ice</span> zone is the most complex to model. The physical appearance of sea <span class="hlt">ice</span> in the marginal <span class="hlt">ice</span> zone varies. Grease <span class="hlt">ice</span>, pancake <span class="hlt">ice</span>, brash <span class="hlt">ice</span>, floe aggregates, and continuous <span class="hlt">ice</span> sheet may be found in this zone at different times and locations. These types of <span class="hlt">ice</span> are formed under different thermal-mechanical forcing. There are three classic models that describe wave propagation through an idealized <span class="hlt">ice</span> cover: <span class="hlt">mass</span> loading, thin elastic plate, and viscous layer models. From physical arguments we may conjecture that <span class="hlt">mass</span> loading model is suitable for disjoint aggregates of <span class="hlt">ice</span> floes much smaller than the wavelength, thin elastic plate model is suitable for a continuous <span class="hlt">ice</span> sheet, and the viscous layer model is suitable for grease <span class="hlt">ice</span>. For different sea <span class="hlt">ice</span> types we may need different wave <span class="hlt">ice</span> interaction models. A recently proposed viscoelastic model is able to synthesize all three classic models into one. Under suitable limiting conditions it converges to the three previous models. The complete theoretical framework for evaluating wave propagation through various <span class="hlt">ice</span> covers need to be implemented in the operational ocean wave models. In this review, we introduce the sea <span class="hlt">ice</span> types, previous wave <span class="hlt">ice</span> interaction models, wave attenuation mechanisms, the methods to calculate wave reflection and transmission between different <span class="hlt">ice</span> covers, and the effect of <span class="hlt">ice</span> floe breaking on shaping the sea <span class="hlt">ice</span> morphology</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28987084','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28987084"><span>Formation and decomposition of CO2-filled <span class="hlt">ice</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Massani, B; Mitterdorfer, C; Loerting, T</p> <p>2017-10-07</p> <p>Recently it was shown that CO 2 -filled <span class="hlt">ice</span> is formed upon compression of CO 2 -clathrate hydrate. Here we show two alternative routes of its formation, namely, by decompression of CO 2 /<span class="hlt">ice</span> VI mixtures at 250 K and by isobaric heating of CO 2 /high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> mixtures at 0.5-1.0 GPa above 200 K. Furthermore, we show that filled <span class="hlt">ice</span> may either transform into the clathrate at an elevated pressure or decompose to "empty" hexagonal <span class="hlt">ice</span> at ambient pressure and low temperature. This complements the literature studies in which decomposition to <span class="hlt">ice</span> VI was favoured at high pressures and low temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JChPh.147m4503M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JChPh.147m4503M"><span>Formation and decomposition of CO2-filled <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Massani, B.; Mitterdorfer, C.; Loerting, T.</p> <p>2017-10-01</p> <p>Recently it was shown that CO2-filled <span class="hlt">ice</span> is formed upon compression of CO2-clathrate hydrate. Here we show two alternative routes of its formation, namely, by decompression of CO2/<span class="hlt">ice</span> VI mixtures at 250 K and by isobaric heating of CO2/high-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> mixtures at 0.5-1.0 GPa above 200 K. Furthermore, we show that filled <span class="hlt">ice</span> may either transform into the clathrate at an elevated pressure or decompose to "empty" hexagonal <span class="hlt">ice</span> at ambient pressure and low temperature. This complements the literature studies in which decomposition to <span class="hlt">ice</span> VI was favoured at high pressures and low temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10393572','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10393572"><span>Effects of true <span class="hlt">density</span>, compacted <span class="hlt">mass</span>, compression speed, and punch deformation on the mean yield pressure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gabaude, C M; Guillot, M; Gautier, J C; Saudemon, P; Chulia, D</p> <p>1999-07-01</p> <p>Compressibility properties of pharmaceutical materials are widely characterized by measuring the volume reduction of a powder column under pressure. Experimental data are commonly analyzed using the Heckel model from which powder deformation mechanisms are determined using mean yield pressure (Py). Several studies from the literature have shown the effects of operating conditions on the determination of Py and have pointed out the limitations of this model. The Heckel model requires true <span class="hlt">density</span> and compacted <span class="hlt">mass</span> values to determine Py from force-displacement data. It is likely that experimental errors will be introduced when measuring the true <span class="hlt">density</span> and compacted <span class="hlt">mass</span>. This study investigates the effects of true <span class="hlt">density</span> and compacted <span class="hlt">mass</span> on Py. Materials having different particle deformation mechanisms are studied. Punch displacement and applied pressure are measured for each material at two compression speeds. For each material, three different true <span class="hlt">density</span> and compacted <span class="hlt">mass</span> values are utilized to evaluate their effect on Py. The calculated variation of Py reaches 20%. This study demonstrates that the errors in measuring true <span class="hlt">density</span> and compacted <span class="hlt">mass</span> have a greater effect on Py than the errors incurred from not correcting the displacement measurements due to punch elasticity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012cosp...39...44A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012cosp...39...44A"><span>Remote Sensing of Cryosphere: Estimation of <span class="hlt">Mass</span> Balance Change in Himalayan Glaciers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ambinakudige, Shrinidhi; Joshi, Kabindra</p> <p>2012-07-01</p> <p>Glacial changes are an important indicator of climate change. Our understanding <span class="hlt">mass</span> balance change in Himalayan glaciers is limited. This study estimates <span class="hlt">mass</span> balance of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. Remote sensing technique to measure <span class="hlt">mass</span> balance of glaciers is an important methodological advance in the highly rugged Himalayan terrain. This study uses ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area for the years 2002, 2003, 2004 and 2005. Glacier boundaries were delineated using combination of boundaries available in the Global land <span class="hlt">ice</span> measurement (GLIMS) database and various band ratios derived from ASTER images. Elevation differences, glacial area, and <span class="hlt">ice</span> <span class="hlt">densities</span> were used to estimate the change in <span class="hlt">mass</span> balance. The results indicated that the rate of glacier <span class="hlt">mass</span> balance change was not uniform across glaciers. While there was a decrease in <span class="hlt">mass</span> balance of some glaciers, some showed increase. This paper discusses how each glacier in the SNP area varied in its annual <span class="hlt">mass</span> balance measurement during the study period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4621R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4621R"><span>State of Arctic Sea <span class="hlt">Ice</span> North of Svalbard during N-<span class="hlt">ICE</span>2015</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rösel, Anja; King, Jennifer; Gerland, Sebastian</p> <p>2016-04-01</p> <p>The N-<span class="hlt">ICE</span>2015 cruise, led by the Norwegian Polar Institute, was a drift experiment with the research vessel R/V Lance from January to June 2015, where the ship started the drift North of Svalbard at 83°14.45' N, 21°31.41' E. The drift was repeated as soon as the vessel drifted free. Altogether, 4 <span class="hlt">ice</span> stations where installed and the complex ocean-sea <span class="hlt">ice</span>-atmosphere system was studied with an interdisciplinary Approach. During the N-<span class="hlt">ICE</span>2015 cruise, extensive <span class="hlt">ice</span> thickness and snow depth measurements were performed during both, winter and summer conditions. Total <span class="hlt">ice</span> and snow thickness was measured with ground-based and airborne electromagnetic instruments; snow depth was measured with a GPS snow depth probe. Additionally, <span class="hlt">ice</span> <span class="hlt">mass</span> balance and snow buoys were deployed. Snow and <span class="hlt">ice</span> thickness measurements were performed on repeated transects to quantify the <span class="hlt">ice</span> growth or loss as well as the snow accumulation and melt rate. Additionally, we collected independent values on surveys to determine the general <span class="hlt">ice</span> thickness distribution. Average snow depths of 32 cm on first year <span class="hlt">ice</span>, and 52 cm on multi-year <span class="hlt">ice</span> were measured in January, the mean snow depth on all <span class="hlt">ice</span> types even increased until end of March to 49 cm. The average total <span class="hlt">ice</span> and snow thickness in winter conditions was 1.92 m. During winter we found a small growth rate on multi-year <span class="hlt">ice</span> of about 15 cm in 2 months, due to above-average snow depths and some extraordinary storm events that came along with mild temperatures. In contrast thereto, we also were able to study new <span class="hlt">ice</span> formation and thin <span class="hlt">ice</span> on newly formed leads. In summer conditions an enormous melt rate, mainly driven by a warm Atlantic water inflow in the marginal <span class="hlt">ice</span> zone, was observed during two <span class="hlt">ice</span> stations with melt rates of up to 20 cm per 24 hours. To reinforce the local measurements around the ship and to confirm their significance on a larger scale, we compare them to airborne thickness measurements and classified SAR-satellite scenes. The</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51E..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51E..07C"><span>Investigation of Controls on <span class="hlt">Ice</span> Dynamics in Northeast Greenland from <span class="hlt">Ice</span>-Thickness Change Record Using <span class="hlt">Ice</span> Sheet System Model (ISSM)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Csatho, B. M.; Larour, E. Y.; Schenk, A. F.; Schlegel, N.; Duncan, K.</p> <p>2015-12-01</p> <p>We present a new, complete <span class="hlt">ice</span> thickness change reconstruction of the NE sector of the Greenland <span class="hlt">Ice</span> Sheet for 1978-2014, partitioned into changes due to surface processes and <span class="hlt">ice</span> dynamics. Elevation changes are computed from all available stereoscopic DEMs, and laser altimetry data (ICESat, ATM, LVIS). Surface <span class="hlt">Mass</span> Balance and firn-compaction estimates are from RACMO2.3. Originating nearly at the divide of the Greenland <span class="hlt">Ice</span> Sheet (GrIS), the dynamically active North East <span class="hlt">Ice</span> Stream (NEGIS) is capable of rapidly transmitting <span class="hlt">ice</span>-marginal forcing far inland. Thus, NEGIS provides a possible mechanism for a rapid drawdown of <span class="hlt">ice</span> from the <span class="hlt">ice</span> sheet interior as marginal warming, thinning and retreat continues. Our altimetry record shows accelerating dynamic thinning of Zachariæ Isstrom, initially limited to the deepest part of the fjord near the calving front (1978-2000) and then extending at least 75 km inland. At the same time, changes over the Nioghalvfjerdsfjorden (N79) Glacier are negligible. We also detect localized large dynamic changes at higher elevations on the <span class="hlt">ice</span> sheet. These thickness changes, often occurring at the onset of fast flow, could indicate rapid variations of basal lubrication due to rerouting of subglacial drainage. We investigate the possible causes of the observed spatiotemporal pattern of <span class="hlt">ice</span> sheet elevation changes using the <span class="hlt">Ice</span> Sheet System Model (ISSM). This work build on our previous studies examining the sensitivity of <span class="hlt">ice</span> flow within the Northeast Greenland <span class="hlt">Ice</span> Stream (NEGIS) to key fields, including <span class="hlt">ice</span> viscosity, basal drag. We assimilate the new altimetry record into ISSM to improve the reconstruction of basal friction and <span class="hlt">ice</span> viscosity. Finally, airborne geophysical (gravity, magnetic) and <span class="hlt">ice</span>-penetrating radar data is examined to identify the potential geologic controls on the <span class="hlt">ice</span> thickness change pattern. Our study provides the first comprehensive reconstruction of <span class="hlt">ice</span> thickness changes for the entire NEGIS drainage basin during</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002775&hterms=inversion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dinversion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002775&hterms=inversion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dinversion"><span>Spatial and Temporal Antarctic <span class="hlt">Ice</span> Sheet <span class="hlt">Mass</span> Trends, Glacio-Isostatic Adjustment, and Surface Processes from a Joint Inversion of Satellite Altimeter, Gravity, and GPS Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin-Espanol, Alba; Zammit-Mangion, Andrew; Clarke, Peter J.; Flament, Thomas; Helm, Veit; King, Matt A.; Luthcke, Scott B.; Petrie, Elizabeth; Remy, Frederique; Schon, Nana; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170002775'); toggleEditAbsImage('author_20170002775_show'); toggleEditAbsImage('author_20170002775_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170002775_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170002775_hide"></p> <p>2016-01-01</p> <p>We present spatiotemporal <span class="hlt">mass</span> balance trends for the Antarctic <span class="hlt">Ice</span> Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003-2013. Our method simultaneously determines annual trends in <span class="hlt">ice</span> dynamics, surface <span class="hlt">mass</span> balance anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003-2013, Antarctica has been losing <span class="hlt">mass</span> at a rateof -84 +/- 22 Gt per yr, with a sustained negative mean trend of dynamic imbalance of -111 +/- 13 Gt per yr. West Antarctica is the largest contributor with -112 +/- 10 Gt per yr, mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in <span class="hlt">mass</span> loss in the last decade, with a mean rate of -28 +/- 7 Gt per yr and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total <span class="hlt">mass</span> loss is partly compensated by a significant <span class="hlt">mass</span> gain of 56 +/- 18 Gt per yr in East Antarctica due to a positive trend of surface <span class="hlt">mass</span> balance anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C44A..03Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C44A..03Y"><span>Greenland <span class="hlt">ice</span> sheet beyond 2100: Simulating its evolution and influence using the coupled climate-<span class="hlt">ice</span> sheet model EC-Earth - PISM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, S.; Christensen, J. H.; Madsen, M. S.; Ringgaard, I. M.; Petersen, R. A.; Langen, P. P.</p> <p>2017-12-01</p> <p>Greenland <span class="hlt">ice</span> sheet (GrIS) is observed undergoing a rapid change in the recent decades, with an increasing area of surface melting and ablation and a speeding <span class="hlt">mass</span> loss. Predicting the GrIS changes and their climate consequences relies on the understanding of the interaction of the GrIS with the climate system on both global and local scales, and requires climate model systems incorporating with an explicit and physically consistent <span class="hlt">ice</span> sheet module. In this work we study the GrIS evolution and its interaction with the climate system using a fully coupled global climate model with a dynamical <span class="hlt">ice</span> sheet model for the GrIS. The coupled model system, EC-EARTH - PISM, consisting of the atmosphere-ocean-sea <span class="hlt">ice</span> model system EC-EARTH, and the Parallel <span class="hlt">Ice</span> Sheet Model (PISM), has been employed for a 1400-year simulation forced by CMIP5 historical forcing from 1850 to 2005 and continued along an extended RCP8.5 scenario with the forcing peaking at 2200 and stabilized hereafter. The simulation reveals that, following the anthropogenic forcing increase, the global mean surface temperature rapidly rises about 10 °C in the 21st and 22nd century. After the forcing stops increasing after 2200, the temperature change slows down and eventually stabilizes at about 12.5 °C above the preindustrial level. In response to the climate warming, the GrIS starts losing <span class="hlt">mass</span> slowly in the 21st century, but the <span class="hlt">ice</span> retreat accelerates substantially after 2100 and <span class="hlt">ice</span> <span class="hlt">mass</span> loss continues hereafter at a constant rate of approximately 0.5 m sea level rise equivalence per 100 years, even as the warming rate gradually levels off. Ultimately the volume and extent of GrIS reduce to less than half of its preindustrial value. To understand the interaction of GrIS with the climate system, the characteristics of atmospheric and oceanic circulation in the warm climate are analyzed. The circulation patterns associated with the negative surface <span class="hlt">mass</span> balance that leads to GrIS retreat are investigated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24858957','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24858957"><span>Theory of amorphous <span class="hlt">ices</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Limmer, David T; Chandler, David</p> <p>2014-07-01</p> <p>We derive a phase diagram for amorphous solids and liquid supercooled water and explain why the amorphous solids of water exist in several different forms. Application of large-deviation theory allows us to prepare such phases in computer simulations. Along with nonequilibrium transitions between the ergodic liquid and two distinct amorphous solids, we establish coexistence between these two amorphous solids. The phase diagram we predict includes a nonequilibrium triple point where two amorphous phases and the liquid coexist. Whereas the amorphous solids are long-lived and slowly aging glasses, their melting can lead quickly to the formation of crystalline <span class="hlt">ice</span>. Further, melting of the higher <span class="hlt">density</span> amorphous solid at low pressures takes place in steps, transitioning to the lower-<span class="hlt">density</span> glass before accessing a nonequilibrium liquid from which <span class="hlt">ice</span> coarsens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4084464','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4084464"><span>Theory of amorphous <span class="hlt">ices</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Limmer, David T.; Chandler, David</p> <p>2014-01-01</p> <p>We derive a phase diagram for amorphous solids and liquid supercooled water and explain why the amorphous solids of water exist in several different forms. Application of large-deviation theory allows us to prepare such phases in computer simulations. Along with nonequilibrium transitions between the ergodic liquid and two distinct amorphous solids, we establish coexistence between these two amorphous solids. The phase diagram we predict includes a nonequilibrium triple point where two amorphous phases and the liquid coexist. Whereas the amorphous solids are long-lived and slowly aging glasses, their melting can lead quickly to the formation of crystalline <span class="hlt">ice</span>. Further, melting of the higher <span class="hlt">density</span> amorphous solid at low pressures takes place in steps, transitioning to the lower-<span class="hlt">density</span> glass before accessing a nonequilibrium liquid from which <span class="hlt">ice</span> coarsens. PMID:24858957</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24910517','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24910517"><span>A century of variation in the dependence of Greenland iceberg calving on <span class="hlt">ice</span> sheet surface <span class="hlt">mass</span> balance and regional climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bigg, G R; Wei, H L; Wilton, D J; Zhao, Y; Billings, S A; Hanna, E; Kadirkamanathan, V</p> <p>2014-06-08</p> <p>Iceberg calving is a major component of the total <span class="hlt">mass</span> balance of the Greenland <span class="hlt">ice</span> sheet (GrIS). A century-long record of Greenland icebergs comes from the International <span class="hlt">Ice</span> Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland. I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades. In this study, we show, through a combination of nonlinear system identification and coupled ocean-iceberg modelling, that I48N's variability is predominantly caused by fluctuation in GrIS calving discharge rather than open ocean iceberg melting. We also demonstrate that the episodic variation in iceberg discharge is strongly linked to a nonlinear combination of recent changes in the surface <span class="hlt">mass</span> balance (SMB) of the GrIS and regional atmospheric and oceanic climate variability, on the scale of the previous 1-3 years, with the dominant causal mechanism shifting between glaciological (SMB) and climatic (ocean temperature) over time. We suggest that this is a change in whether glacial run-off or under-<span class="hlt">ice</span> melting is dominant, respectively. We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5738V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5738V"><span>The Tweeting <span class="hlt">Ice</span> Shelf: geophysics and outreach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Liefferinge, Brice; Berger, Sophie; Drews, Reinhard; Pattyn, Frank</p> <p>2015-04-01</p> <p>Over the last decade the Antarctic and Greenland <span class="hlt">ice</span> sheets have contributed about one third of the annual sea level rise (Hanna et al., 2013). However, it remains difficult to reconcile global <span class="hlt">mass</span> balance estimates obtained from different satellite-based methods. A typical approach is to balance the <span class="hlt">mass</span> input from atmospheric modelling with the outgoing <span class="hlt">mass</span> flux at the <span class="hlt">ice</span>-sheet boundary (Shepherd et al., 2012). The flux calculations at the boundary rely on satellite-derived surface velocities, which are currently only available as snapshots in time, and which need ground truth for validation. Here, we report on continuous, year-round measurements that aim at improving the input-output method in several aspects and carefully map the flow speed allowing for detecting seasonal variability. For this purpose, we set up in December 2014 three stand-alone single-frequency GPSes on the Roi Baudouin <span class="hlt">ice</span> shelf (East Antarctica). The GPSes are installed across a surface depression (typical for large <span class="hlt">ice</span>-shelf channels), where subglacial melting is expected. This setup allows us to investigate how these channels behave, i.e., if they become wider, whether or not they enhance the <span class="hlt">ice</span> flow, and, in combination with an installed phase-sensitive radar, what amount of melting occurs below the channels in contact with the ocean. The GPS data are transmitted on a daily basis. <span class="hlt">Ice</span>-shelf velocity is derived from the raw hourly location following the methods described in den Ouden et al. (2010), Dunse et al. (2012), and Ahlstrøm et al. (2013). However, a reference station has not been used for the correction. Basic processing involves outliers removal, smoothing, time-series analysis and comparison with tidal models. The project comes alongside an outreach event: on a weekly basis, the <span class="hlt">ice</span> shelf 'tweets' its position, motion and relays other information with respect to the project. The GPS systems can be followed on Twitter via @Tweetin<span class="hlt">Ice</span>Shelf as well as the Tweeting <span class="hlt">Ice</span> Shelf</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26526560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26526560"><span>Investigation of Aerosol Surface Area Estimation from Number and <span class="hlt">Mass</span> Concentration Measurements: Particle <span class="hlt">Density</span> Effect.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ku, Bon Ki; Evans, Douglas E</p> <p>2012-04-01</p> <p>For nanoparticles with nonspherical morphologies, e.g., open agglomerates or fibrous particles, it is expected that the actual <span class="hlt">density</span> of agglomerates may be significantly different from the bulk material <span class="hlt">density</span>. It is further expected that using the material <span class="hlt">density</span> may upset the relationship between surface area and <span class="hlt">mass</span> when a method for estimating aerosol surface area from number and <span class="hlt">mass</span> concentrations (referred to as "Maynard's estimation method") is used. Therefore, it is necessary to quantitatively investigate how much the Maynard's estimation method depends on particle morphology and <span class="hlt">density</span>. In this study, aerosol surface area estimated from number and <span class="hlt">mass</span> concentration measurements was evaluated and compared with values from two reference methods: a method proposed by Lall and Friedlander for agglomerates and a mobility based method for compact nonspherical particles using well-defined polydisperse aerosols with known particle <span class="hlt">densities</span>. Polydisperse silver aerosol particles were generated by an aerosol generation facility. Generated aerosols had a range of morphologies, count median diameters (CMD) between 25 and 50 nm, and geometric standard deviations (GSD) between 1.5 and 1.8. The surface area estimates from number and <span class="hlt">mass</span> concentration measurements correlated well with the two reference values when gravimetric <span class="hlt">mass</span> was used. The aerosol surface area estimates from the Maynard's estimation method were comparable to the reference method for all particle morphologies within the surface area ratios of 3.31 and 0.19 for assumed GSDs 1.5 and 1.8, respectively, when the bulk material <span class="hlt">density</span> of silver was used. The difference between the Maynard's estimation method and surface area measured by the reference method for fractal-like agglomerates decreased from 79% to 23% when the measured effective particle <span class="hlt">density</span> was used, while the difference for nearly spherical particles decreased from 30% to 24%. The results indicate that the use of particle <span class="hlt">density</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRC..117.9031G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRC..117.9031G"><span>Modeling the basal melting and marine <span class="hlt">ice</span> accretion of the Amery <span class="hlt">Ice</span> Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galton-Fenzi, B. K.; Hunter, J. R.; Coleman, R.; Marsland, S. J.; Warner, R. C.</p> <p>2012-09-01</p> <p>The basal <span class="hlt">mass</span> balance of the Amery <span class="hlt">Ice</span> Shelf (AIS) in East Antarctica is investigated using a numerical ocean model. The main improvements of this model over previous studies are the inclusion of frazil formation and dynamics, tides and the use of the latest estimate of the sub-<span class="hlt">ice</span>-shelf cavity geometry. The model produces a net basal melt rate of 45.6 Gt year-1 (0.74 m <span class="hlt">ice</span> year-1) which is in good agreement with reviewed observations. The melting at the base of the <span class="hlt">ice</span> shelf is primarily due to interaction with High Salinity Shelf Water created from the surface sea-<span class="hlt">ice</span> formation in winter. The temperature difference between the coldest waters created in the open ocean and the in situ freezing point of ocean water in contact with the deepest part of the AIS drives a melt rate that can exceed 30 m of <span class="hlt">ice</span> year-1. The inclusion of frazil dynamics is shown to be important for both melting and marine <span class="hlt">ice</span> accretion (refreezing). Frazil initially forms in the supercooled water layer adjacent to the base of the <span class="hlt">ice</span> shelf. The net accretion of marine <span class="hlt">ice</span> is 5.3 Gt year-1, comprised of 3.7 Gt year-1 of frazil accretion and 1.6 Gt year-1 of direct basal refreezing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvE..90b2711K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvE..90b2711K"><span>Dynamical mechanism of antifreeze proteins to prevent <span class="hlt">ice</span> growth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kutschan, B.; Morawetz, K.; Thoms, S.</p> <p>2014-08-01</p> <p>The fascinating ability of algae, insects, and fishes to survive at temperatures below normal freezing is realized by antifreeze proteins (AFPs). These are surface-active molecules and interact with the diffusive water-<span class="hlt">ice</span> interface thus preventing complete solidification. We propose a dynamical mechanism on how these proteins inhibit the freezing of water. We apply a Ginzburg-Landau-type approach to describe the phase separation in the two-component system (<span class="hlt">ice</span>, AFP). The free-energy <span class="hlt">density</span> involves two fields: one for the <span class="hlt">ice</span> phase with a low AFP concentration and one for liquid water with a high AFP concentration. The time evolution of the <span class="hlt">ice</span> reveals microstructures resulting from phase separation in the presence of AFPs. We observed a faster clustering of pre-<span class="hlt">ice</span> structure connected to a locking of grain size by the action of AFP, which is an essentially dynamical process. The adsorption of additional water molecules is inhibited and the further growth of <span class="hlt">ice</span> grains stopped. The interfacial energy between <span class="hlt">ice</span> and water is lowered allowing the AFPs to form smaller critical <span class="hlt">ice</span> nuclei. Similar to a hysteresis in magnetic materials we observe a thermodynamic hysteresis leading to a nonlinear <span class="hlt">density</span> dependence of the freezing point depression in agreement with the experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvL.119m5701L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvL.119m5701L"><span>Kinetically Controlled Two-Step Amorphization and Amorphous-Amorphous Transition in <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Chuanlong; Yong, Xue; Tse, John S.; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kenney-Benson, Curtis; Shen, Guoyin</p> <p>2017-09-01</p> <p>We report the results of in situ structural characterization of the amorphization of crystalline <span class="hlt">ice</span> Ih under compression and the relaxation of high-<span class="hlt">density</span> amorphous (HDA) <span class="hlt">ice</span> under decompression at temperatures between 96 and 160 K by synchrotron x-ray diffraction. The results show that <span class="hlt">ice</span> Ih transforms to an intermediate crystalline phase at 100 K prior to complete amorphization, which is supported by molecular dynamics calculations. The phase transition pathways show clear temperature dependence: direct amorphization without an intermediate phase is observed at 133 K, while at 145 K a direct Ih-to-IX transformation is observed; decompression of HDA shows a transition to low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> at 96 K and ˜1 Pa , to <span class="hlt">ice</span> Ic at 135 K and to <span class="hlt">ice</span> IX at 145 K. These observations show that the amorphization of compressed <span class="hlt">ice</span> Ih and the recrystallization of decompressed HDA are strongly dependent on temperature and controlled by kinetic barriers. Pressure-induced amorphous <span class="hlt">ice</span> is an intermediate state in the phase transition from the connected H-bond water network in low pressure <span class="hlt">ices</span> to the independent and interpenetrating H-bond network of high-pressure <span class="hlt">ices</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1397299-kinetically-controlled-two-step-amorphization-amorphous-amorphous-transition-ice','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1397299-kinetically-controlled-two-step-amorphization-amorphous-amorphous-transition-ice"><span>Kinetically Controlled Two-Step Amorphization and Amorphous-Amorphous Transition in <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Lin, Chuanlong; Yong, Xue; Tse, John S.</p> <p></p> <p>We report the results of in situ structural characterization of the amorphization of crystalline <span class="hlt">ice</span> Ih under compression and the relaxation of high-<span class="hlt">density</span> amorphous (HDA) <span class="hlt">ice</span> under decompression at temperatures between 96 and 160 K by synchrotron x-ray diffraction. The results show that <span class="hlt">ice</span> Ih transforms to an intermediate crystalline phase at 100 K prior to complete amorphization, which is supported by molecular dynamics calculations. The phase transition pathways show clear temperature dependence: direct amorphization without an intermediate phase is observed at 133 K, while at 145 K a direct Ih-to-IX transformation is observed; decompression of HDA shows a transitionmore » to low-<span class="hlt">density</span> amorphous <span class="hlt">ice</span> at 96 K and ~ 1 Pa , to <span class="hlt">ice</span> Ic at 135 K and to <span class="hlt">ice</span> IX at 145 K. These observations show that the amorphization of compressed <span class="hlt">ice</span> Ih and the recrystallization of decompressed HDA are strongly dependent on temperature and controlled by kinetic barriers. Pressure-induced amorphous <span class="hlt">ice</span> is an intermediate state in the phase transition from the connected H-bond water network in low pressure <span class="hlt">ices</span> to the independent and interpenetrating H-bond network of high-pressure <span class="hlt">ices</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C13F1017M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C13F1017M"><span>Atmospheric river impacts on Greenland <span class="hlt">Ice</span> Sheet surface melt and <span class="hlt">mass</span> balance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mattingly, K.; Mote, T. L.</p> <p>2017-12-01</p> <p><span class="hlt">Mass</span> loss from the Greenland <span class="hlt">Ice</span> Sheet (GrIS) has accelerated during the early part of the 21st Century. Several episodes of widespread GrIS melt in recent years have coincided with intense poleward moisture transport by atmospheric rivers (ARs), suggesting that variability in the frequency and intensity of these events may be an important driver of the surface <span class="hlt">mass</span> balance (SMB) of the GrIS. ARs may contribute to GrIS surface melt through the greenhouse effect of water vapor, the radiative effects of clouds, condensational latent heating within poleward-advected air <span class="hlt">masses</span>, and the energy provided by liquid precipitation. However, ARs may also provide significant positive contributions to GrIS SMB through enhanced snow accumulation. Prior research on the role of ARs in Arctic climate has consisted of case studies of ARs associated with major GrIS melt events or examined the effects of poleward moisture flux on Arctic sea <span class="hlt">ice</span>. In this study, a long-term (1979-2016) record of intense moisture transport events affecting Greenland is compiled using a conventional AR identification algorithm as well as a self-organizing map (SOM) classification applied to integrated water vapor transport (IVT) data from several atmospheric reanalysis datasets. An analysis of AR effects on GrIS melt and SMB is then performed with GrIS surface melt data from passive microwave satellite observations and the Modèle Atmosphérique Régional (MAR) regional climate model. Results show that meltwater production is above normal during and after AR impact days throughout the GrIS during all seasons, with surface melt enhanced most by strong (> 85th percentile IVT) and extreme (> 95th percentile IVT) ARs. This relationship holds at the seasonal scale, as the total amount of water vapor transported to the GrIS by ARs is significantly greater during above-normal melt seasons. ARs exert a more complex influence on SMB. Normal (< 85th percentile IVT) ARs generally do not have a substantial impact on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.U11A..06W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.U11A..06W"><span>Albedo of bare <span class="hlt">ice</span> near the Trans-Antarctic Mountains to represent sea-glaciers on the tropical ocean of Snowball Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Warren, S. G.; Dadic, R.; Mullen, P.; Schneebeli, M.; Brandt, R. E.</p> <p>2012-12-01</p> <p>The albedos of snow and <span class="hlt">ice</span> surfaces are, because of their positive feedback, crucial to the initiation, maintenance, and termination of a snowball event, as well as for determining the <span class="hlt">ice</span> thickness on the ocean. Despite the name, Snowball Earth would not have been entirely snow-covered. As on modern Earth, evaporation would exceed precipitation over much of the tropical ocean. After a transient period with sea <span class="hlt">ice</span>, the dominant <span class="hlt">ice</span> type would probably be sea-glaciers flowing in from higher latitude. As they flowed equatorward into the tropical region of net sublimation, their surface snow and subsurface firn would sublimate away, exposing bare glacier <span class="hlt">ice</span> to the atmosphere and to solar radiation. This <span class="hlt">ice</span> would be freshwater (meteoric) <span class="hlt">ice</span>, which originated from snow and firn, so it would contain numerous air bubbles, which determine the albedo. The modern surrogate for this type of <span class="hlt">ice</span> (glacier <span class="hlt">ice</span> exposed by sublimation, which has never experienced melting), are the bare-<span class="hlt">ice</span> surfaces of the Antarctic <span class="hlt">Ice</span> Sheet near the Trans-Antarctic Mountains. These areas have been well mapped because of their importance in the search for meteorites. A transect across an icefield can sample <span class="hlt">ice</span> of different ages that has traveled to different depths en route to the sublimation front. On a 6-km transect from snow to <span class="hlt">ice</span> near the Allan Hills, spectral albedo was measured and 1-m core samples were collected. This short transect is meant to represent a north-south transect across many degrees of latitude on the snowball ocean. Surfaces on the transect transitioned through the sequence: new snow - old snow - firn - young white <span class="hlt">ice</span> - old blue <span class="hlt">ice</span>. The transect from snow to <span class="hlt">ice</span> showed a systematic progression of decreasing albedo at all wavelengths, as well as decreasing specific surface area (SSA; ratio of air-<span class="hlt">ice</span> interface area to <span class="hlt">ice</span> <span class="hlt">mass</span>) and increasing <span class="hlt">density</span>. The measured spectral albedos are integrated over wavelength and weighted by the spectral solar flux to obtain</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23274717','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23274717"><span><span class="hlt">Mass</span> carbon monoxide poisoning at an <span class="hlt">ice</span>-hockey game: initial approach and long-term follow-up.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mortelmans, Luc J M; Populaire, Jacques; Desruelles, Didier; Sabbe, Marc B</p> <p>2013-12-01</p> <p>A <span class="hlt">mass</span> carbon monoxide (CO) intoxication during an <span class="hlt">ice</span>-hockey game is described. Two hundred and thirty-five patients were seen in different hospitals, 88 of them the same night at the nearby emergency department. To evaluate long-term implications and to identify relevant indicators, a follow-up study was organized 1 year after the incident. Apart from the file data from the emergency departments, a 1-year follow-up mailing was sent to all patients. One hundred and ninety-one patients returned their questionnaire (86%). The mean age of the patients was 28 years, with 61% men. The mean carboxyhaemoglobin (COHb) was 9.9%. COHb levels were significantly higher for individuals on the <span class="hlt">ice</span> (referee, players and maintenance personnel). There was a significant relationship with the initial presence of dizziness, fatigue and the COHb level. Headache, abdominal pain, nausea and vomiting were not significantly related to the COHb levels. The relationship between symptoms and CO level, however, should be interpreted with caution as there was a wide range between exposure and blood tests. 5.2% of patients had residual complaints, all including headache, with a significant higher incidence with high COHb levels. Only two patients had an abnormal neurological control (one slightly disturbed electroencephalography and one persistent encephalopathic complaint). Work incapacity was also significantly related to COHb levels. CO <span class="hlt">mass</span> poisonings remain a risk in indoor sporting events. Although it causes an acute <span class="hlt">mass</span> casualty incident, it is limited in time and delayed problems are scarce. Symptomatology is a poor tool for triage. The best prevention is the use of nonmineral energy sources such as for example electricity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830034350&hterms=drainage+blocked&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddrainage%2Bblocked','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830034350&hterms=drainage+blocked&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddrainage%2Bblocked"><span><span class="hlt">Ice</span> sculpture in the Martian outflow channels</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lucchitta, B. K.</p> <p>1982-01-01</p> <p>Viking Orbiter and terrestrial satellite images are examined at similar resolution to compare features of the Martian outflow channels with features produced by the movement of <span class="hlt">ice</span> on earth, and many resemblances are found. These include the anastomoses, sinuosities, and U-shaped cross profiles of valleys; hanging valleys; linear scour marks on valley walls; grooves and ridges on valley floors; and the streamlining of bedrock highs. Attention is given to the question whether <span class="hlt">ice</span> could have moved in the Martian environment. It is envisaged that springs or small catastrophic outbursts discharged fluids from structural outlets or chaotic terrains. These fluids built <span class="hlt">icings</span> that may have grown into substantial <span class="hlt">masses</span> and eventually flowed like glaciers down preexisting valleys. An alternative is that the fluids formed rivers or floods that in turn formed <span class="hlt">ice</span> jams and consolidated into icy <span class="hlt">masses</span> in places where obstacles blocked their flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080018456&hterms=Secret&qs=N%3D0%26Ntk%3DTitle%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThe%2BSecret','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080018456&hterms=Secret&qs=N%3D0%26Ntk%3DTitle%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThe%2BSecret"><span>The Secret of the Svalbard Sea <span class="hlt">Ice</span> Barrier</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nghiem, Son V.; Van Woert, Michael L.; Neumann, Gregory</p> <p>2004-01-01</p> <p>An elongated sea <span class="hlt">ice</span> feature called the Svalbard sea <span class="hlt">ice</span> barrier rapidly formed over an area in the Barents Sea to the east of Svalbard posing navigation hazards. The secret of its formation lies in the bottom bathymetry that governs the distribution of cold Arctic waters <span class="hlt">masses</span>, which impacts sea <span class="hlt">ice</span> growth on the water surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/990526-global-simulations-ice-nucleation-ice-supersaturation-improved-cloud-scheme-community-atmosphere-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/990526-global-simulations-ice-nucleation-ice-supersaturation-improved-cloud-scheme-community-atmosphere-model"><span>Global Simulations of <span class="hlt">Ice</span> nucleation and <span class="hlt">Ice</span> Supersaturation with an Improved Cloud Scheme in the Community Atmosphere Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Gettelman, A.; Liu, Xiaohong; Ghan, Steven J.</p> <p>2010-09-28</p> <p>A process-based treatment of <span class="hlt">ice</span> supersaturation and <span class="hlt">ice</span>-nucleation is implemented in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to <span class="hlt">ice</span>, (2) <span class="hlt">ice</span> nucleation by aerosol particles and (3) <span class="hlt">ice</span> cloud cover consistent with <span class="hlt">ice</span> microphysics. The scheme is implemented with a 4-class 2 moment microphysics code and is used to evaluate <span class="hlt">ice</span> cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of <span class="hlt">ice</span> <span class="hlt">mass</span> and mixed phase cloud occurrence better than previous versions of the model. Simulations indicatemore » heterogeneous freezing and contact nucleation on dust are both potentially important over remote areas of the Arctic. Cloud forcing and hence climate is sensitive to different formulations of the <span class="hlt">ice</span> microphysics. Arctic radiative fluxes are sensitive to the parameterization of <span class="hlt">ice</span> clouds. These results indicate that <span class="hlt">ice</span> clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032359','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032359"><span>A tale of two polar bear populations: <span class="hlt">Ice</span> habitat, harvest, and body condition</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Rode, Karyn D.; Peacock, Elizabeth; Taylor, Mitchell K.; Stirling, Ian; Born, Erik W.; Laidre, Kristin L.; Wiig, Øystein</p> <p>2012-01-01</p> <p>One of the primary mechanisms by which sea <span class="hlt">ice</span> loss is expected to affect polar bears is via reduced body condition and growth resulting from reduced access to prey. To date, negative effects of sea <span class="hlt">ice</span> loss have been documented for two of 19 recognized populations. Effects of sea <span class="hlt">ice</span> loss on other polar bear populations that differ in harvest rate, population <span class="hlt">density</span>, and/or feeding ecology have been assumed, but empirical support, especially quantitative data on population size, demography, and/or body condition spanning two or more decades, have been lacking. We examined trends in body condition metrics of captured bears and relationships with summertime <span class="hlt">ice</span> concentration between 1977 and 2010 for the Baffin Bay (BB) and Davis Strait (DS) polar bear populations. Polar bears in these regions occupy areas with annual sea <span class="hlt">ice</span> that has decreased markedly starting in the 1990s. Despite differences in harvest rate, population <span class="hlt">density</span>, sea <span class="hlt">ice</span> concentration, and prey base, polar bears in both populations exhibited positive relationships between body condition and summertime sea <span class="hlt">ice</span> cover during the recent period of sea <span class="hlt">ice</span> decline. Furthermore, females and cubs exhibited relationships with sea <span class="hlt">ice</span> that were not apparent during the earlier period (1977–1990s) when sea <span class="hlt">ice</span> loss did not occur. We suggest that declining body condition in BB may be a result of recent declines in sea <span class="hlt">ice</span> habitat. In DS, high population <span class="hlt">density</span> and/or sea <span class="hlt">ice</span> loss, may be responsible for the declines in body condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29390815','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29390815"><span>Kinetic boundaries and phase transformations of <span class="hlt">ice</span> i at high pressure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Yu; Zhang, Huichao; Yang, Xue; Jiang, Shuqing; Goncharov, Alexander F</p> <p>2018-01-28</p> <p>Raman spectroscopy in diamond anvil cells has been employed to study phase boundaries and transformation kinetics of H 2 O <span class="hlt">ice</span> at high pressures up to 16 GPa and temperatures down to 15 K. <span class="hlt">Ice</span> i formed at nearly isobaric cooling of liquid water transforms on compression to high-<span class="hlt">density</span> amorphous (HDA) <span class="hlt">ice</span> at 1.1-3 GPa at 15-100 K and then crystallizes in <span class="hlt">ice</span> vii with the frozen-in disorder (<span class="hlt">ice</span> vii') which remains stable up to 14.1 GPa at 80 K and 15.9 GPa at 100 K. Unexpectedly, on decompression of <span class="hlt">ice</span> vii', it transforms to <span class="hlt">ice</span> viii in its domain of metastability, and then it relaxes into low-<span class="hlt">density</span> amorphous (LDA) <span class="hlt">ice</span> on a subsequent pressure release and warming up. On compression of <span class="hlt">ice</span> i at 150-170 K, <span class="hlt">ice</span> ix is crystallized and no HDA <span class="hlt">ice</span> is found; further compression of <span class="hlt">ice</span> ix results in the sequential phase transitions to stable <span class="hlt">ices</span> vi and viii. Cooling <span class="hlt">ice</span> i to 210 K at 0.3 GPa transforms it to a stable <span class="hlt">ice</span> ii. Our extensive investigations provide previously missing information on the phase diagram of water, especially on the kinetic paths that result in formation of phases which otherwise are not accessible; these results are keys for understanding the phase relations including the formation of metastable phases. Our observations inform on the <span class="hlt">ice</span> modifications that can occur naturally in planetary environments and are not accessible for direct observations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JChPh.148d4508W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JChPh.148d4508W"><span>Kinetic boundaries and phase transformations of <span class="hlt">ice</span> i at high pressure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Yu; Zhang, Huichao; Yang, Xue; Jiang, Shuqing; Goncharov, Alexander F.</p> <p>2018-01-01</p> <p>Raman spectroscopy in diamond anvil cells has been employed to study phase boundaries and transformation kinetics of H2O <span class="hlt">ice</span> at high pressures up to 16 GPa and temperatures down to 15 K. <span class="hlt">Ice</span> i formed at nearly isobaric cooling of liquid water transforms on compression to high-<span class="hlt">density</span> amorphous (HDA) <span class="hlt">ice</span> at 1.1-3 GPa at 15-100 K and then crystallizes in <span class="hlt">ice</span> vii with the frozen-in disorder (<span class="hlt">ice</span> vii') which remains stable up to 14.1 GPa at 80 K and 15.9 GPa at 100 K. Unexpectedly, on decompression of <span class="hlt">ice</span> vii', it transforms to <span class="hlt">ice</span> viii in its domain of metastability, and then it relaxes into low-<span class="hlt">density</span> amorphous (LDA) <span class="hlt">ice</span> on a subsequent pressure release and warming up. On compression of <span class="hlt">ice</span> i at 150-170 K, <span class="hlt">ice</span> ix is crystallized and no HDA <span class="hlt">ice</span> is found; further compression of <span class="hlt">ice</span> ix results in the sequential phase transitions to stable <span class="hlt">ices</span> vi and viii. Cooling <span class="hlt">ice</span> i to 210 K at 0.3 GPa transforms it to a stable <span class="hlt">ice</span> ii. Our extensive investigations provide previously missing information on the phase diagram of water, especially on the kinetic paths that result in formation of phases which otherwise are not accessible; these results are keys for understanding the phase relations including the formation of metastable phases. Our observations inform on the <span class="hlt">ice</span> modifications that can occur naturally in planetary environments and are not accessible for direct observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4115C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4115C"><span>Antarctic <span class="hlt">ice</span> shelf thickness from CryoSat-2 radar altimetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chuter, Stephen; Bamber, Jonathan</p> <p>2016-04-01</p> <p>The Antarctic <span class="hlt">ice</span> shelves provide buttressing to the inland grounded <span class="hlt">ice</span> sheet, and therefore play a controlling role in regulating <span class="hlt">ice</span> dynamics and <span class="hlt">mass</span> imbalance. Accurate knowledge of <span class="hlt">ice</span> shelf thickness is essential for input-output method <span class="hlt">mass</span> balance calculations, sub-<span class="hlt">ice</span> shelf ocean models and buttressing parameterisations in <span class="hlt">ice</span> sheet models. <span class="hlt">Ice</span> shelf thickness has previously been inferred from satellite altimetry elevation measurements using the assumption of hydrostatic equilibrium, as direct measurements of <span class="hlt">ice</span> thickness do not provide the spatial coverage necessary for these applications. The sensor limitations of previous radar altimeters have led to poor data coverage and a lack of accuracy, particularly the grounding zone where a break in slope exists. We present a new <span class="hlt">ice</span> shelf thickness dataset using four years (2011-2014) of CryoSat-2 elevation measurements, with its SARIn dual antennae mode of operation alleviating the issues affecting previous sensors. These improvements and the dense across track spacing of the satellite has resulted in ˜92% coverage of the <span class="hlt">ice</span> shelves, with substantial improvements, for example, of over 50% across the Venable and Totten <span class="hlt">Ice</span> Shelves in comparison to the previous dataset. Significant improvements in coverage and accuracy are also seen south of 81.5° for the Ross and Filchner-Ronne <span class="hlt">Ice</span> Shelves. Validation of the surface elevation measurements, used to derive <span class="hlt">ice</span> thickness, against NASA ICESat laser altimetry data shows a mean bias of less than 1 m (equivalent to less than 9 m in <span class="hlt">ice</span> thickness) and a fourfold decrease in standard deviation in comparison to the previous continental dataset. Importantly, the most substantial improvements are found in the grounding zone. Validation of the derived thickness data has been carried out using multiple Radio Echo Sounding (RES) campaigns across the continent. Over the Amery <span class="hlt">ice</span> shelf, where extensive RES measurements exist, the mean difference between the datasets is 3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.430..427R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.430..427R"><span>Modelling the feedbacks between <span class="hlt">mass</span> balance, <span class="hlt">ice</span> flow and debris transport to predict the response to climate change of debris-covered glaciers in the Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rowan, Ann V.; Egholm, David L.; Quincey, Duncan J.; Glasser, Neil F.</p> <p>2015-11-01</p> <p>Many Himalayan glaciers are characterised in their lower reaches by a rock debris layer. This debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean-<span class="hlt">ice</span> surfaces. Debris-covered glaciers can persist well below the altitude that would be sustainable for clean-<span class="hlt">ice</span> glaciers, resulting in much longer timescales of <span class="hlt">mass</span> loss and meltwater production. The properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change. Existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean-<span class="hlt">ice</span> surfaces, and yield conflicting results. We developed a numerical model that couples the flow of <span class="hlt">ice</span> and debris and includes important feedbacks between debris accumulation and glacier <span class="hlt">mass</span> balance. To investigate the impact of debris transport on the response of a glacier to recent and future climate change, we applied this model to a large debris-covered Himalayan glacier-Khumbu Glacier in Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ, concealing the magnitude of <span class="hlt">mass</span> loss when compared with estimates based on glacierised area. Since the Little <span class="hlt">Ice</span> Age, Khumbu Glacier has lost 34% of its volume while its area has reduced by only 6%. We predict a decrease in glacier volume of 8-10% by AD2100, accompanied by dynamic and physical detachment of the debris-covered tongue from the active glacier within the next 150 yr. This detachment will accelerate rates of glacier decay, and similar changes are likely for other debris-covered glaciers in the Himalaya.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.A43B0199C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.A43B0199C"><span>Partitioning CloudSat <span class="hlt">Ice</span> Water Content for Comparison with Upper-Tropospheric <span class="hlt">Ice</span> in Global Atmospheric Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, W. A.; Woods, C. P.; Li, J. F.; Waliser, D. E.; Chern, J.; Tao, W.; Jiang, J. H.; Tompkins, A. M.</p> <p>2010-12-01</p> <p>CloudSat provides important estimates of vertically resolved <span class="hlt">ice</span> water content (IWC) on a global scale based on radar reflectivity. These estimates of IWC have proven beneficial in evaluating the representations of <span class="hlt">ice</span> clouds in global models. An issue when performing model-data comparisons of IWC particularly germane to this investigation, is the question of which component(s) of the frozen water <span class="hlt">mass</span> are represented by retrieval estimates and how they relate to what is represented in models. The present study developed and applied a new technique to partition CloudSat total IWC into small and large <span class="hlt">ice</span> hydrometeors, based on the CloudSat-retrieved <span class="hlt">ice</span> particle size distribution (PSD) parameters. The new method allows one to make relevant model-data comparisons and provides new insights into the model’s representation of atmospheric IWC. The partitioned CloudSat IWC suggests that the small <span class="hlt">ice</span> particles contribute to 20-30% of the total IWC in the upper troposphere when a threshold size of 100 μm is used. Sensitivity measures with respect to the threshold size, the PSD parameters, and the retrieval algorithms are presented. The new dataset is compared to model estimates, pointing to areas for model improvement. Cloud <span class="hlt">ice</span> analyses from the European Centre for Medium-Range Weather Forecasts model agree well with the small IWC from CloudSat. The finite-volume multi-scale modeling framework model underestimates total IWC at 147 and 215 hPa, while overestimating the fractional contribution from the small <span class="hlt">ice</span> species. These results are discussed in terms of their applications to, and implications for, the evaluation of global atmospheric models, providing constraints on the representations of cloud feedback and precipitation in global models, which in turn can help reduce uncertainties associated with climate change projections. Figure 1. A sample lognormal <span class="hlt">ice</span> number distribution (red curve), and the corresponding <span class="hlt">mass</span> distribution (black curve). The dotted line</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24322733','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24322733"><span>Infrared and reflectron time-of-flight <span class="hlt">mass</span> spectroscopic analysis of methane (CH4)-carbon monoxide (CO) <span class="hlt">ices</span> exposed to ionization radiation--toward the formation of carbonyl-bearing molecules in extraterrestrial <span class="hlt">ices</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kaiser, Ralf I; Maity, Surajit; Jones, Brant M</p> <p>2014-02-28</p> <p><span class="hlt">Ice</span> mixtures of methane and carbon monoxide were exposed to ionizing radiation in the form of energetic electrons at 5.5 K to investigate the formation of carbonyl bearing molecules in extraterrestrial <span class="hlt">ices</span>. The radiation induced chemical processing of the mixed <span class="hlt">ices</span> along with their isotopically labeled counterparts was probed online and in situ via infrared spectroscopy (solid state) aided with reflectron time-of-flight <span class="hlt">mass</span> spectrometry (ReTOFMS) coupled to single photon photoionization (PI) at 10.49 eV (gas phase). Deconvolution of the carbonyl absorption feature centered at 1727 cm(-1) in the processed <span class="hlt">ices</span> and subsequent kinetic fitting to the temporal growth of the newly formed species suggests the formation of acetaldehyde (CH3CHO) together with four key classes of carbonyl-bearing molecules: (i) alkyl aldehydes, (ii) alkyl ketones, (iii) α,β-unsaturated ketones/aldehydes and (iv) α,β,γ,δ-unsaturated ketones/α,β-dicarbonyl compounds in keto-enol form. The mechanistical studies indicate that acetaldehyde acts as the key building block of higher aldehydes (i) and ketones (ii) with unsaturated ketones/aldehydes (iii) and/or α,β-dicarbonyl compounds (iv) formed from the latter. Upon sublimation of the newly synthesized molecules, ReTOFMS together with isotopic shifts of the <span class="hlt">mass</span>-to-charge ratios was exploited to identify eleven product classes containing molecules with up to six carbon atoms, which can be formally derived from C1-C5 hydrocarbons incorporating up to three carbon monoxide building blocks. The classes are (i) saturated aldehydes/ketones, (ii) unsaturated aldehydes/ketones, (iii) doubly unsaturated aldehydes/ketones, (iv) saturated dicarbonyls (aldehydes/ketones), (v) unsaturated dicarbonyls (aldehydes/ketones), (vi) saturated tricarbonyls (aldehydes/ketones), molecules containing (vii) one carbonyl - one alcohol (viii), two carbonyls - one alcohol, (ix) one carbonyl - two alcohol groups along with (x) alcohols and (xi) diols. Reaction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.1177S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.1177S"><span>Glacier <span class="hlt">mass</span> balance in high-arctic areas with anomalous gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharov, A.; Rieser, D.; Nikolskiy, D.</p> <p>2012-04-01</p> <p>All known glaciological models describing the evolution of Arctic land- and sea-<span class="hlt">ice</span> <span class="hlt">masses</span> in changing climate treat the Earth's gravity as horizontally constant, but it isn't. In the High Arctic, the strength of the gravitational field varies considerably across even short distances under the influence of a <span class="hlt">density</span> gradient, and the magnitude of free air gravity anomalies attains 100 mGal and more. On long-term base, instantaneous deviations of gravity can have a noticeable effect on the regime and <span class="hlt">mass</span> budget of glaciological objects. At best, the gravity-induced component of <span class="hlt">ice</span> <span class="hlt">mass</span> variations can be determined on topographically smooth, open and steady surfaces, like those of arctic planes, regular <span class="hlt">ice</span> caps and landfast sea <span class="hlt">ice</span>. The present research is devoted to studying gravity-driven impacts on glacier <span class="hlt">mass</span> balance in the outer periphery of four Eurasian shelf seas with a very cold, dry climate and rather episodic character of winter precipitation. As main study objects we had chosen a dozen Russia's northernmost insular <span class="hlt">ice</span> caps, tens to hundreds of square kilometres in extent, situated in a close vicinity of strong gravity anomalies and surrounded with extensive fields of fast and/or drift <span class="hlt">ice</span> for most of the year. The supposition about gravitational forcing on glacioclimatic settings in the study region is based on the results of quantitative comparison and joint interpretation of existing glacier change maps and available data on the Arctic gravity field and solid precipitation. The overall mapping of medium-term (from decadal to half-centennial) changes in glacier volumes and quantification of <span class="hlt">mass</span> balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1980s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. Free-air gravity anomalies were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.B21F..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.B21F..01H"><span>Pedogenesis on <span class="hlt">ice</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hodson, A. J.</p> <p>2010-12-01</p> <p>It is well known from <span class="hlt">ice</span> cores that organic and mineral debris accumulates within glacier <span class="hlt">ice</span> following atmospheric deposition. However, the concentrations of such debris are usually greatest upon the <span class="hlt">ice</span> surface, especially at the margins of continental glaciers and <span class="hlt">ice</span> sheets, where it forms mm-scale aggregate particles called “cryoconite”. According to the literature, cryoconite covers about 2 % of the ablation areas of glaciers outside Greenland and Antarctica, equivalent to a <span class="hlt">mass</span> loading of ca. 25 g/m2. Of the great <span class="hlt">ice</span> sheets not included in this figure, Greenland is the easiest to estimate, and new observations from the NE and SW sectors indicate <span class="hlt">mass</span> loadings in the range 17 - 440 g/m2. Studies of cryoconite often report the presence of a significant biomass (usually 10^4 - 10^7 cells/g) that is capable of a wide range of biogeochemical functions. The first part of this presentation will therefore explore the contention that the formation of cryoconite represents the first stages of pedogenesis, resulting in the production of soil-type aggregates that inoculate glacial forefields following glacier retreat. Emphasis will be given to the relevant processes that result in aggregate formation, including rapid cell-mineral attachment within melting snowpacks and the slower, biological processes of cementation within thermodynamically stable habitats such as cryoconite holes. The second part of the presentation will use examples from Svalbard, Greenland and Antarctica to consider the carbon balance of the cryoconite during the longest phase of its life cycle: upon the <span class="hlt">ice</span>. It will be demonstrated how the efficacy of photosynthesis is strongly influenced by thermodynamic conditions at or near this surface. Data from the Greenland and Antarctic <span class="hlt">ice</span> sheets will show how thermal equilibration decouples variations in photosynthesis from variations in incident radiation over timescales > 1 d, resulting in an equitable, low-carbon economy for aggregates within</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1573J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1573J"><span>Coupled <span class="hlt">ice</span> sheet-ocean modelling to investigate ocean driven melting of marine <span class="hlt">ice</span> sheets in Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jong, Lenneke; Gladstone, Rupert; Galton-Fenzi, Ben</p> <p>2017-04-01</p> <p>Ocean induced melting below the <span class="hlt">ice</span> shelves of marine <span class="hlt">ice</span> sheets is a major source of uncertainty for predictions of <span class="hlt">ice</span> <span class="hlt">mass</span> loss and Antarctica's resultant contribution to future sea level rise. The floating <span class="hlt">ice</span> shelves provide a buttressing force against the flow of <span class="hlt">ice</span> across the grounding line into the ocean. Thinning of these <span class="hlt">ice</span> shelves due to an increase in melting reduces this force and can lead to an increase in the discharge of grounded <span class="hlt">ice</span>. Fully coupled modelling of <span class="hlt">ice</span> sheet-ocean interactions is key to improving understanding the influence of the Southern ocean on the evolution of the Antarctic <span class="hlt">ice</span> sheet, and to predicting its future behaviour under changing climate conditions. Coupling of ocean and <span class="hlt">ice</span> sheet models is needed to provide more realistic melt rates at the base of <span class="hlt">ice</span> shelves and hence make better predictions of the behaviour of the grounding line and the shape of the <span class="hlt">ice</span>-shelf cavity as the <span class="hlt">ice</span> sheet evolves. The Framework for <span class="hlt">Ice</span> Sheet - Ocean Coupling (FISOC) has been developed to provide a flexible platform for performing coupled <span class="hlt">ice</span> sheet - ocean modelling experiments. We present preliminary results using FISOC to couple the Regional Ocean Modelling System (ROMS) with Elmer/<span class="hlt">Ice</span> in idealised experiments Marine <span class="hlt">Ice</span> Sheet-Ocean Model Intercomparison Project (MISOMIP). These experiments use an idealised geometry motivated by that of Pine Island glacier and the adjacent Amundsen Sea in West Antarctica, a region which has shown shown signs of thinning <span class="hlt">ice</span> and grounding line retreat.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870027099&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870027099&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmicrowaves%2Bwater%2Bstructure"><span>Satellite microwave and in situ observations of the Weddell Sea <span class="hlt">ice</span> cover and its marginal <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Comiso, J. C.; Sullivan, C. W.</p> <p>1986-01-01</p> <p>The radiative and physical characteristics of the Weddell Sea <span class="hlt">ice</span> cover and its marginal <span class="hlt">ice</span> zone are analyzed using multichannel satellite passive microwave data and ship and helicopter observations obtained during the 1983 Antarctic Marine Ecosystem Research. Winter and spring brightness temperatures are examined; spatial variability in the brightness temperatures of consolidated <span class="hlt">ice</span> in winter and spring cyclic increases and decrease in brightness temperatures of consolidated <span class="hlt">ice</span> with an amplitude of 50 K at 37 GHz and 20 K at 18 GHz are observed. The roles of variations in air temperature and surface characteristics in the variability of spring brightness temperatures are investigated. <span class="hlt">Ice</span> concentrations are derived using the frequency and polarization techniques, and the data are compared with the helicopter and ship observations. Temporal changes in the <span class="hlt">ice</span> margin structure and the <span class="hlt">mass</span> balance of fresh water and of biological features of the marginal <span class="hlt">ice</span> zone are studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4931510','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4931510"><span>Partially ordered state of <span class="hlt">ice</span> XV</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Komatsu, K.; Noritake, F.; Machida, S.; Sano-Furukawa, A.; Hattori, T.; Yamane, R.; Kagi, H.</p> <p>2016-01-01</p> <p>Most <span class="hlt">ice</span> polymorphs have order–disorder “pairs” in terms of hydrogen positions, which contributes to the rich variety of <span class="hlt">ice</span> polymorphs; in fact, three recently discovered polymorphs— <span class="hlt">ices</span> XIII, XIV, and XV—are ordered counter forms to already identified disordered phases. Despite the considerable effort to understand order–disorder transition in <span class="hlt">ice</span> crystals, there is an inconsistency among the various experiments and calculations for <span class="hlt">ice</span> XV, the ordered counter form of <span class="hlt">ice</span> VI, i.e., neutron diffraction observations suggest antiferroelectrically ordered structures, which disagree with dielectric measurement and theoretical studies, implying ferroelectrically ordered structures. Here we investigate in-situ neutron diffraction measurements and <span class="hlt">density</span> functional theory calculations to revisit the structure and stability of <span class="hlt">ice</span> XV. We find that none of the completely ordered configurations are particular favored; instead, partially ordered states are established as a mixture of ordered domains in disordered <span class="hlt">ice</span> VI. This scenario in which several kinds of ordered configuration coexist dispels the contradictions in previous studies. It means that the order–disorder pairs in <span class="hlt">ice</span> polymorphs are not one-to-one correspondent pairs but rather have one-to-n correspondence, where there are n possible configurations at finite temperature. PMID:27375120</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C54A..02H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C54A..02H"><span><span class="hlt">Ice</span> shelf thickness change from 2010 to 2017</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hogg, A.; Shepherd, A.; Gilbert, L.; Muir, A. S.</p> <p>2017-12-01</p> <p>Floating <span class="hlt">ice</span> shelves fringe 74 % of Antarctica's coastline, providing a direct link between the <span class="hlt">ice</span> sheet and the surrounding oceans. Over the last 25 years, <span class="hlt">ice</span> shelves have retreated, thinned, and collapsed catastrophically. While change in the <span class="hlt">mass</span> of floating <span class="hlt">ice</span> shelves has only a modest steric impact on the rate of sea-level rise, their loss can affect the <span class="hlt">mass</span> balance of the grounded <span class="hlt">ice</span>-sheet by influencing the rate of <span class="hlt">ice</span> flow inland, due to the buttressing effect. Here we use CryoSat-2 altimetry data to map the detailed pattern of <span class="hlt">ice</span> shelf thickness change in Antarctica. We exploit the dense spatial sampling and repeat coverage provided by the CryoSat-2 synthetic aperture radar interferometric mode (SARIn) to investigate data acquired between 2010 to the present day. We find that <span class="hlt">ice</span> shelf thinning rates can exhibit large fluctuations over short time periods, and that the improved spatial resolution of CryoSat-2 enables us to resolve the spatial pattern of thinning with ever greater detail in Antarctica. In the Amundsen Sea, <span class="hlt">ice</span> shelves at the terminus of the Pine Island and Thwaites glaciers have thinned at rates in excess of 5 meters per year for more than two decades. We observe the highest rates of basal melting near to the <span class="hlt">ice</span> sheet grounding line, reinforcing the importance of high resolution datasets. On the Antarctic Peninsula, in contrast to the 3.8 m per decade of thinning observed since 1992, we measure an increase in the surface elevation of the Larsen-C <span class="hlt">Ice</span>-Shelf during the CryoSat-2 period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70038745','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70038745"><span>History of the Greenland <span class="hlt">Ice</span> Sheet: paleoclimatic insights</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Alley, Richard B.; Andrews, John T.; Brigham-Grette, J.; Clarke, G.K.C.; Cuffey, Kurt M.; Fitzpatrick, J.J.; Funder, S.; Marshall, S.J.; Miller, G.H.; Mitrovica, J.X.; Muhs, D.R.; Otto-Bliesner, B. L.; Polyak, L.; White, J.W.C.</p> <p>2010-01-01</p> <p>Paleoclimatic records show that the Greenland<span class="hlt">Ice</span> Sheet consistently has lost <span class="hlt">mass</span> in response to warming, and grown in response to cooling. Such changes have occurred even at times of slow or zero sea-level change, so changing sea level cannot have been the cause of at least some of the <span class="hlt">ice</span>-sheet changes. In contrast, there are no documented major <span class="hlt">ice</span>-sheet changes that occurred independent of temperature changes. Moreover, snowfall has increased when the climate warmed, but the <span class="hlt">ice</span> sheet lost <span class="hlt">mass</span> nonetheless; increased accumulation in the <span class="hlt">ice</span> sheet's center has not been sufficient to counteract increased melting and flow near the edges. Most documented forcings and <span class="hlt">ice</span>-sheet responses spanned periods of several thousand years, but limited data also show rapid response to rapid forcings. In particular, regions near the <span class="hlt">ice</span> margin have responded within decades. However, major changes of central regions of the <span class="hlt">ice</span> sheet are thought to require centuries to millennia. The paleoclimatic record does not yet strongly constrain how rapidly a major shrinkage or nearly complete loss of the <span class="hlt">ice</span> sheet could occur. The evidence suggests nearly total <span class="hlt">ice</span>-sheet loss may result from warming of more than a few degrees above mean 20th century values, but this threshold is poorly defined (perhaps as little as 2 °C or more than 7 °C). Paleoclimatic records are sufficiently sketchy that the <span class="hlt">ice</span> sheet may have grown temporarily in response to warming, or changes may have been induced by factors other than temperature, without having been recorded.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.amap.no/documents/doc/snow-water-ice-and-permafrost-in-the-arctic-swipa-climate-change-and-the-cryosphere/743','USGSPUBS'); return false;" href="http://www.amap.no/documents/doc/snow-water-ice-and-permafrost-in-the-arctic-swipa-climate-change-and-the-cryosphere/743"><span>Mountain Glaciers and <span class="hlt">Ice</span> Caps</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.</p> <p>2011-01-01</p> <p>Projections of future rates of <span class="hlt">mass</span> loss from mountain glaciers and <span class="hlt">ice</span> caps in the Arctic focus primarily on projections of changes in the surface <span class="hlt">mass</span> balance. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface <span class="hlt">mass</span> balance models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, <span class="hlt">mass</span> loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface <span class="hlt">mass</span> balance model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total <span class="hlt">mass</span> loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier <span class="hlt">mass</span> in the Arctic in 2100 and that Arctic mountain glaciers and <span class="hlt">ice</span> caps will continue to influence global sea-level change well into the 22nd century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918710V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918710V"><span>A Transient Initialization Routine of the Community <span class="hlt">Ice</span> Sheet Model for the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Laan, Larissa; van den Broeke, Michiel; Noël, Brice; van de Wal, Roderik</p> <p>2017-04-01</p> <p>The Community <span class="hlt">Ice</span> Sheet Model (CISM) is to be applied in future simulations of the Greenland <span class="hlt">Ice</span> Sheet under a range of climate change scenarios, determining the sensitivity of the <span class="hlt">ice</span> sheet to individual climatic forcings. In order to achieve reliable results regarding <span class="hlt">ice</span> sheet stability and assess the probability of future occurrence of tipping points, a realistic initial <span class="hlt">ice</span> sheet geometry is essential. The current work describes and evaluates the development of a transient initialization routine, using NGRIP 18O isotope data to create a temperature anomaly field. Based on the latter, surface <span class="hlt">mass</span> balance components runoff and precipitation are perturbed for the past 125k years. The precipitation and runoff fields originate from a downscaled 1 km resolution version of the regional climate model RACMO2.3 for the period 1961-1990. The result of the initialization routine is a present-day <span class="hlt">ice</span> sheet with a transient memory of the last glacial-interglacial cycle, which will serve as the future runs' initial condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860003488','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860003488"><span>Plasma volume methodology: Evans blue, hemoglobin-hematocrit, and <span class="hlt">mass</span> <span class="hlt">density</span> transformations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greenleaf, J. E.; Hinghofer-Szalkay, H.</p> <p>1985-01-01</p> <p>Methods for measuring absolute levels and changes in plasma volume are presented along with derivations of pertinent equations. Reduction in variability of the Evans blue dye dilution technique using chromatographic column purification suggests that the day-to-day variability in the plasma volume in humans is less than + or - 20 m1. <span class="hlt">Mass</span> <span class="hlt">density</span> determination using the mechanical-oscillator technique provides a method for measuring vascular fluid shifts continuously for assessing the <span class="hlt">density</span> of the filtrate, and for quantifying movements of protein across microvascular walls. Equations for the calculation of volume and <span class="hlt">density</span> of shifted fluid are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030004821','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030004821"><span>ICESat: <span class="hlt">Ice</span>, Cloud and Land Elevation Satellite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwally, Jay; Shuman, Christopher</p> <p>2002-01-01</p> <p><span class="hlt">Ice</span> exists in the natural environment in many forms. The Earth dynamic <span class="hlt">ice</span> features shows that at high elevations and/or high latitudes,snow that falls to the ground can gradually build up tu form thick consolidated <span class="hlt">ice</span> <span class="hlt">masses</span> called glaciers. Glaciers flow downhill under the force of gravity and can extend into areas that are too warm to support year-round snow cover. The snow line, called the equilibrium line on a glacier or <span class="hlt">ice</span> sheet, separates the <span class="hlt">ice</span> areas that melt on the surface and become show free in summer (net ablation zone) from the <span class="hlt">ice</span> area that remain snow covered during the entire year (net accumulation zone). Snow near the surface of a glacier that is gradually being compressed into solid <span class="hlt">ice</span> is called firm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA159060','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA159060"><span>Marginal <span class="hlt">Ice</span> Zone Bibliography.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1985-06-01</p> <p>A Voyage of Discovery. George Deacon 70th An-niversary Volume, (M. Angel, ed.), Pergamon Press, Oxford, p.15-41. Coachman, L.K., C.A. Barnes, 1961...some polar contrasts. In: S "" RUsium on Antarctic <span class="hlt">Ice</span> and Water <span class="hlt">Masses</span>, ( George Deacon, ed.), Sci- 72 Lebedev, A.A., 1968: Zone of possible <span class="hlt">icing</span> of...Atlantic and Western Europe. British Meteorological Office. Geophysical Memoirs, 4(41). Brost , R.A., J.C. Wyngaard, 1978: A model study of the stably</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29066736','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29066736"><span>Enhanced <span class="hlt">ice</span> sheet melting driven by volcanic eruptions during the last deglaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Muschitiello, Francesco; Pausata, Francesco S R; Lea, James M; Mair, Douglas W F; Wohlfarth, Barbara</p> <p>2017-10-24</p> <p>Volcanic eruptions can impact the <span class="hlt">mass</span> balance of <span class="hlt">ice</span> sheets through changes in climate and the radiative properties of the <span class="hlt">ice</span>. Yet, empirical evidence highlighting the sensitivity of ancient <span class="hlt">ice</span> sheets to volcanism is scarce. Here we present an exceptionally well-dated annual glacial varve chronology recording the melting history of the Fennoscandian <span class="hlt">Ice</span> Sheet at the end of the last deglaciation (∼13,200-12,000 years ago). Our data indicate that abrupt <span class="hlt">ice</span> melting events coincide with volcanogenic aerosol emissions recorded in Greenland <span class="hlt">ice</span> cores. We suggest that enhanced <span class="hlt">ice</span> sheet runoff is primarily associated with albedo effects due to deposition of ash sourced from high-latitude volcanic eruptions. Climate and snowpack <span class="hlt">mass</span>-balance simulations show evidence for enhanced <span class="hlt">ice</span> sheet runoff under volcanically forced conditions despite atmospheric cooling. The sensitivity of past <span class="hlt">ice</span> sheets to volcanic ashfall highlights the need for an accurate coupling between atmosphere and <span class="hlt">ice</span> sheet components in climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6085044-arctic-ice-shelves-ice-islands-origin-growth-disintegration-physical-characteristics-structural-stratigraphic-variability-dynamics','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6085044-arctic-ice-shelves-ice-islands-origin-growth-disintegration-physical-characteristics-structural-stratigraphic-variability-dynamics"><span>Arctic <span class="hlt">ice</span> shelves and <span class="hlt">ice</span> islands: Origin, growth and disintegration, physical characteristics, structural-stratigraphic variability, and dynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Jeffries, M.O.</p> <p>1992-08-01</p> <p><span class="hlt">Ice</span> shelves are thick, floating <span class="hlt">ice</span> <span class="hlt">masses</span> most often associated with Antarctica where they are seaward extensions of the grounded Antarctic <span class="hlt">ice</span> sheet and sources of many icebergs. However, there are also <span class="hlt">ice</span> shelves in the Arctic, primarily located along the north coast of Ellesmere Island in the Canadian High Arctic. The only <span class="hlt">ice</span> shelves in North America and the most extensive in the north polar region, the Ellesmere <span class="hlt">ice</span> shelves originate from glaciers and from sea <span class="hlt">ice</span> and are the source of <span class="hlt">ice</span> islands, the tabular icebergs of the Arctic Ocean. The present state of knowledge and understanding ofmore » these <span class="hlt">ice</span> features is summarized in this paper. It includes historical background to the discovery and early study of <span class="hlt">ice</span> shelves and <span class="hlt">ice</span> islands, including the use of <span class="hlt">ice</span> islands as floating laboratories for polar geophysical research. Growth mechanisms and age, the former extent and the twentieth century disintegration of the Ellesmere <span class="hlt">ice</span> shelves, and the processes and mechanisms of <span class="hlt">ice</span> island calving are summarized. Surface features, thickness, thermal regime, and the size, shape, and numbers of <span class="hlt">ice</span> islands are discussed. The structural-stratigraphic variability of <span class="hlt">ice</span> islands and <span class="hlt">ice</span> shelves and the complex nature of their growth and development are described. Large-scale and small-scale dynamics of <span class="hlt">ice</span> islands are described, and the results of modeling their drift and recurrence intervals are presented. The conclusion identifies some unanswered questions and future research opportunities and needs. 97 refs., 18 figs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22278127-meta-atom-cluster-acoustic-metamaterial-broadband-negative-effective-mass-density','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22278127-meta-atom-cluster-acoustic-metamaterial-broadband-negative-effective-mass-density"><span>Meta-atom cluster acoustic metamaterial with broadband negative effective <span class="hlt">mass</span> <span class="hlt">density</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chen, Huaijun; Zhai, Shilong; Ding, Changlin</p> <p>2014-02-07</p> <p>We design a resonant meta-atom cluster, via which a two-dimensional (2D) acoustic metamaterial (AM) with broadband negative effective <span class="hlt">mass</span> <span class="hlt">density</span> from 1560 Hz to 5580 Hz is fabricated. Experimental results confirm that there is only weak interaction among the meta-atoms in the cluster. And then the meta-atoms in the cluster independently resonate, resulting in the cluster becoming equivalent to a broadband resonance unit. Extracted effective refractive indices from reflection and transmission measurements of the 2D AM appear to be negative from 1500 Hz to 5480 Hz. The broadband negative refraction has also been demonstrated by our further experiments. We expectmore » that this meta-atom cluster AM will significantly contribute to the design of broadband negative effective <span class="hlt">mass</span> <span class="hlt">density</span> AM.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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