Journal articles on the topic 'Airborne Mass Balance Experiments'
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Konovalov, Yuri V., and Oleg V. Nagornov. "Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap." Earth System Dynamics 8, no. 2 (April 20, 2017): 283–94. http://dx.doi.org/10.5194/esd-8-283-2017.
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Abstract. Prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap on Komsomolets Island, Severnaya Zemlya archipelago, were undertaken in this study. The experiments were based on inversions of basal friction coefficients using a two-dimensional flow-line thermocoupled model and Tikhonov's regularization method. The modeled ice temperature distributions in the cross sections were obtained using ice surface temperature histories that were inverted previously from borehole temperature profiles derived at the summit of the Academy of Sciences Ice Cap and the elevational gradient of ice surface temperature changes (about 6.5 °C km−1). Input data included interferometric synthetic aperture radar (InSAR) ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements, while the surface mass balance was adopted from previous investigations for the implementation of both the forward and inverse problems. The prognostic experiments revealed that both ice mass and ice stream extent declined for the reference time-independent surface mass balance. Specifically, the grounding line retreated: (a) along the B–B′ flow line from ∼ 40 to ∼ 30 km (the distance from the summit), (b) along the C–C′ flow line from ∼ 43 to ∼ 37 km, and (c) along the D–D′ flow line from ∼ 41 to ∼ 32 km, when considering a time period of 500 years and assuming a time-independent surface mass balance. Ice flow velocities in the ice streams decreased with time and this trend resulted in the overall decline of the outgoing ice flux. Generally, the modeled glacial evolution was in agreement with observations of deglaciation of the Severnaya Zemlya archipelago.
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Konovalov, Y. V., and O. V. Nagornov. "Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap: future modeled histories obtained for the reference surface mass balance." Earth System Dynamics Discussions 6, no. 2 (November 3, 2015): 2211–42. http://dx.doi.org/10.5194/esdd-6-2211-2015.
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Abstract. The prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago, are implemented in this study. These experiments are based on inversions of basal friction coefficients using a two-dimensional flow-line thermo-coupled model and the Tikhonov's regularization method. The modeled ice temperature distributions in the cross-sections were obtained using the ice surface temperature histories that were inverted previously from the borehole temperature profiles derived at the Academy of Sciences Ice Cap. Input data included InSAR ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements and the surface mass balance, were adopted from the prior investigations for the implementation of both the forward and inverse problems. The prognostic experiments reveal that both ice mass and ice stream extents decline for the reference time-independent surface mass balance. Specifically, the grounding line retreats (a) along the B–B' flow line from ~ 40 to ~ 30 km (the distance from the summit), (b) along the C–C' flow line from ~ 43 to ~ 37 km, and (c) along the D–D' flow line from ~ 41 to ~ 32 km considering a time period of 500 years and assuming time-independent surface mass balance. Ice flow velocities in the ice streams decrease with time and this trend results in the overall decline of the outgoing ice flux. Generally, the modeled histories are in agreement with observations of sea ice extent and thickness indicating a continual ice decline in the Arctic.
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Schueneman, Melinda K., Benjamin A. Nault, Pedro Campuzano-Jost, Duseong S. Jo, Douglas A. Day, Jason C. Schroder, Brett B. Palm, Alma Hodzic, Jack E. Dibb, and Jose L. Jimenez. "Aerosol pH indicator and organosulfate detectability from aerosol mass spectrometry measurements." Atmospheric Measurement Techniques 14, no. 3 (March 23, 2021): 2237–60. http://dx.doi.org/10.5194/amt-14-2237-2021.
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Abstract. Aerosol sulfate is a major component of submicron particulate matter (PM1). Sulfate can be present as inorganic (mainly ammonium sulfate, AS) or organosulfate (OS). Although OS is thought to be a smaller fraction of total sulfate in most cases, recent literature argues that this may not be the case in more polluted environments. Aerodyne aerosol mass spectrometers (AMSs) measure total submicron sulfate, but it has been difficult to apportion AS vs. OS as the detected ion fragments are similar. Recently, two new methods have been proposed to quantify OS separately from AS with AMS data. We use observations collected during several airborne field campaigns covering a wide range of sources and air mass ages (spanning the continental US, marine remote troposphere, and Korea) and targeted laboratory experiments to investigate the performance and validity of the proposed OS methods. Four chemical regimes are defined to categorize the factors impacting sulfate fragmentation. In polluted areas with high ammonium nitrate concentrations and in remote areas with high aerosol acidity, the decomposition and fragmentation of sulfate in the AMS is influenced by multiple complex effects, and estimation of OS does not seem possible with current methods. In regions with lower acidity (pH > 0) and ammonium nitrate (fraction of total mass < 0.3), the proposed OS methods might be more reliable, although application of these methods often produced nonsensical results. However, the fragmentation of ambient neutralized sulfate varies somewhat within studies, adding uncertainty, possibly due to variations in the effect of organics. Under highly acidic conditions (when calculated pH < 0 and ammonium balance < 0.65), sulfate fragment ratios show a clear relationship with acidity. The measured ammonium balance (and to a lesser extent, the HySOx+ / SOx+ AMS ratio) is a promising indicator of rapid estimation of aerosol pH < 0, including when gas-phase NH3 and HNO3 are not available. These results allow an improved understanding of important intensive properties of ambient aerosols.
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de Caritat, Patrice, Clemens Reimann, Viktor Chekushin, Igor Bogatyrev, Heikki Niskavaara, and Jean Braun. "Mass Balance between Emission and Deposition of Airborne Contaminants." Environmental Science & Technology 31, no. 10 (October 1997): 2966–72. http://dx.doi.org/10.1021/es970193z.
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Koenig, Lora S., Alvaro Ivanoff, Patrick M. Alexander, Joseph A. MacGregor, Xavier Fettweis, Ben Panzer, John D. Paden, et al. "Annual Greenland accumulation rates (2009–2012) from airborne snow radar." Cryosphere 10, no. 4 (August 11, 2016): 1739–52. http://dx.doi.org/10.5194/tc-10-1739-2016.
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Abstract. Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2–6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009–2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.
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Pelto, Ben M., Brian Menounos, and Shawn J. Marshall. "Multi-year evaluation of airborne geodetic surveys to estimate seasonal mass balance, Columbia and Rocky Mountains, Canada." Cryosphere 13, no. 6 (June 26, 2019): 1709–27. http://dx.doi.org/10.5194/tc-13-1709-2019.
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Abstract. Seasonal measurements of glacier mass balance provide insight into the relation between climate forcing and glacier change. To evaluate the feasibility of using remotely sensed methods to assess seasonal balance, we completed tandem airborne laser scanning (ALS) surveys and field-based glaciological measurements over a 4-year period for six alpine glaciers that lie in the Columbia and Rocky Mountains, near the headwaters of the Columbia River, British Columbia, Canada. We calculated annual geodetic balance using coregistered late summer digital elevation models (DEMs) and distributed estimates of density based on surface classification of ice, snow, and firn surfaces. Winter balance was derived using coregistered late summer and spring DEMs, as well as density measurements from regional snow survey observations and our glaciological measurements. Geodetic summer balance was calculated as the difference between winter and annual balance. Winter mass balance from our glaciological observations averaged 1.95±0.09 m w.e. (meter water equivalent), 4 % larger than those derived from geodetic surveys. Average glaciological summer and annual balance were 3 % smaller and 3 % larger, respectively, than our geodetic estimates. We find that distributing snow, firn, and ice density based on surface classification has a greater influence on geodetic annual mass change than the density values themselves. Our results demonstrate that accurate assessments of seasonal mass change can be produced using ALS over a series of glaciers spanning several mountain ranges. Such agreement over multiple seasons, years, and glaciers demonstrates the ability of high-resolution geodetic methods to increase the number of glaciers where seasonal mass balance can be reliably estimated.
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Bamber, Jonathan L., William Krabill, Vivienne Raper, Julian A. Dowdeswell, and J. Oerlemans. "Elevation changes measured on Svalbard glaciers and ice caps from airborne laser data." Annals of Glaciology 42 (2005): 202–8. http://dx.doi.org/10.3189/172756405781813131.
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AbstractPrecise airborne laser surveys were conducted during spring in 1996 and 2002 on 17 ice caps and glaciers in the Svalbard archipelago covering the islands of Spitsbergen and Nordaustlandet. We present the derived elevation changes. Lower-elevation glaciers in south Spitsbergen show the largest thinning rates of ∼ 0.5 m a-1, while some of the higher, more northerly ice caps appear to be close to balance. The pattern of elevation change is complex, however, due to several factors including glacier aspect, microclimatological influences and the high natural annual variability in local accumulation and ablation rates. Anomalous changes were observed on Fridtjovbreen, which started surging in 1996, at the start of the measurement period. On this glacier, thinning (of > 0.6 m a-1) was observed in the accumulation area, coincident with thickening at lower elevations. Asymmetric thinning was found on two ice caps on Nordaustlandet, with the largest values on the eastern side of Vestfonna but the western slopes of Vegafonna. The mean elevation change for all ice masses was -0.19 m a-1 w.e., which is 1.6 times the net mass-balance value determined for the last 30 years. Using mass-balance sensitivity estimates for Svalbard suggests that the implied increase in negative balance is linked to warmer air temperatures in the late 1990s. Multiple linear regression suggests that mass balance is most closely correlated with latitude, rather than mean altitude or longitude.
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Lewis, Gabriel, Erich Osterberg, Robert Hawley, Brian Whitmore, Hans Peter Marshall, and Jason Box. "Regional Greenland accumulation variability from Operation IceBridge airborne accumulation radar." Cryosphere 11, no. 2 (March 23, 2017): 773–88. http://dx.doi.org/10.5194/tc-11-773-2017.
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Abstract. The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge accumulation radar flights totaling > 17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100–300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a−1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GrIS surface mass balance estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.
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Khaksar, Gholamreza, Dian Siswanto, Chairat Treesubsuntorn, and Paitip Thiravetyan. "Euphorbia milii-Endophytic Bacteria Interactions Affect Hormonal Levels of the Native Host Differently Under Various Airborne Pollutants." Molecular Plant-Microbe Interactions® 29, no. 9 (September 2016): 663–73. http://dx.doi.org/10.1094/mpmi-06-16-0117-r.
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This study was conducted to assess the effect of plant–native endophytic bacteria interactions on indole-3-acetic acid (IAA), ethylene levels, and hormonal balance of Euphorbia milii under different airborne pollutants. IAA levels and airborne formaldehyde removal by E. milii enhanced when inoculated with endophytic isolates. However, one isolate, designated as root endophyte 4, with the highest levels of IAA production individually, declined gaseous formaldehyde removal of plant, since it disturbed hormonal balance of E. milii, leading to IAA levels higher than physiological concentrations, which stimulated ethylene biosynthesis and stomatal closure under light conditions. However, plant–root endophyte 4 interactions favored airborne benzene removal, since benzene was more phytotoxic and the plant needed more IAA to protect against benzene phytotoxicity. As trimethylamine (TMA) was not toxic, it did not affect plant-endophyte interactions. Therefore, IAA levels of root endophyte 4–inoculated E. milii was not significantly different from a noninoculated one. Under mixed-pollutant stress (formaldehyde, benzene, TMA), root endophyte 4–inoculated E. milii removed benzene at the lowest rate, since benzene was the most phytotoxic pollutant with the greatest molecular mass. However, TMA (with greater molecular mass) was removed faster than formaldehyde due to higher phytotoxicity of formaldehyde. Plant-endophyte interactions were affected differently under various airborne pollutants.
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Kuipers Munneke, Peter, Daniel McGrath, Brooke Medley, Adrian Luckman, Suzanne Bevan, Bernd Kulessa, Daniela Jansen, et al. "Observationally constrained surface mass balance of Larsen C ice shelf, Antarctica." Cryosphere 11, no. 6 (November 1, 2017): 2411–26. http://dx.doi.org/10.5194/tc-11-2411-2017.
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Abstract. The surface mass balance (SMB) of the Larsen C ice shelf (LCIS), Antarctica, is poorly constrained due to a dearth of in situ observations. Combining several geophysical techniques, we reconstruct spatial and temporal patterns of SMB over the LCIS. Continuous time series of snow height (2.5–6 years) at five locations allow for multi-year estimates of seasonal and annual SMB over the LCIS. There is high interannual variability in SMB as well as spatial variability: in the north, SMB is 0.40 ± 0.06 to 0.41 ± 0.04 m w.e. year−1, while farther south, SMB is up to 0.50 ± 0.05 m w.e. year−1. This difference between north and south is corroborated by winter snow accumulation derived from an airborne radar survey from 2009, which showed an average snow thickness of 0.34 m w.e. north of 66° S, and 0.40 m w.e. south of 68° S. Analysis of ground-penetrating radar from several field campaigns allows for a longer-term perspective of spatial variations in SMB: a particularly strong and coherent reflection horizon below 25–44 m of water-equivalent ice and firn is observed in radargrams collected across the shelf. We propose that this horizon was formed synchronously across the ice shelf. Combining snow height observations, ground and airborne radar, and SMB output from a regional climate model yields a gridded estimate of SMB over the LCIS. It confirms that SMB increases from north to south, overprinted by a gradient of increasing SMB to the west, modulated in the west by föhn-induced sublimation. Previous observations show a strong decrease in firn air content toward the west, which we attribute to spatial patterns of melt, refreezing, and densification rather than SMB.
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Vargas, Freddy A., and Néstor Y. Rojas. "Chemical composition and mass closure for airborne particulate matter in Bogotá." Ingeniería e Investigación 30, no. 2 (May 1, 2010): 105–15. http://dx.doi.org/10.15446/ing.investig.v30n2.15741.
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Particulate matter, measured as PM10, is the most concerning airborne pollutant in Bogotá. Determining its chemical composition is important for understanding its potential effects and to estimate various sources' contribution to such pollution. This paper gives the results of characterising the ionic species, carbonaceous material, metals and crustal elements present in airborne PM10 in Bogotá. An ion charge balance and mass reconstruction were done for determining consistency between chemical characterisation and gravimetric PM10. The composition was different in each area; however, the fractions contributing most to PM10 were crustal, 37% to 42% was related to fugitive and suspended dust, 12% to 11% was related to carbonaceous fractions, 43% to elemental carbon, 34% for organic matter and 5% to 8% for ionic fractions.
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Colgan, W., W. Abdalati, M. Citterio, B. Csatho, X. Fettweis, S. Luthcke, G. Moholdt, and M. Stober. "Hybrid inventory, gravimetry and altimetry (HIGA) mass balance product for Greenland and the Canadian Arctic." Cryosphere Discussions 8, no. 1 (January 23, 2014): 537–80. http://dx.doi.org/10.5194/tcd-8-537-2014.
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Abstract. We present a novel inversion algorithm that generates a mass balance field that is simultaneously consistent with independent observations of glacier inventory derived from optical imagery, cryosphere-attributed mass changes derived from satellite gravimetry, and ice surface elevation changes derived from airborne and satellite altimetry. We use this algorithm to assess mass balance across Greenland and the Canadian Arctic over the December 2003 to December 2010 period at 26 km resolution. We assess a total mass loss of 316 ± 37 Gt a−1 over Greenland and the Canadian Arctic, with 217 ± 20 Gt a−1 being attributed to the Greenland Ice Sheet proper, and 38 ± 6 Gt a−1 and 50 ± 8 Gt a−1 being attributed to peripheral glaciers in Greenland and the Canadian Arctic, respectively. These absolute values are dependent on the gravimetry-derived spherical harmonic representation we invert. Our attempt to validate local values of algorithm-inferred mass balance reveals a paucity of in situ observations. At four sites, where direct comparison between algorithm-inferred and in situ mass balance is valid, we find an RMSD of 0.18 m WE a−1. Differencing algorithm-inferred mass balance with previously modelled surface mass balance, in order to solve the ice dynamic portion of mass balance as a residual, allows the transient glacier continuity equation to be spatially partitioned across Greenland.
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Bindschadler, Robert, Patricia Vornberger, Donald Blankenship, Ted Scambos, and Robert Jacobel. "Surface velocity and mass balance of Ice Streams D and E, West Antarctica." Journal of Glaciology 42, no. 142 (1996): 461–75. http://dx.doi.org/10.3189/s0022143000003452.
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AbstractOver 75 000 surface-velocity measurements are extracted from sequential satellite imagery of Ice Streams D and E to reveal a complex pattern of flow not apparent from previous measurements. Horizontal and vertical strain rates, calculated from surface velocity, indicate that the bed experiences larger basal shear where the surface of these ice streams is rougher. Ten airborne-radar profiles and one surface-based radar profile of ice thickness make possible the calculation of mass balance for longitudinal sections of each ice stream. Improved data-collection methods increase data density, substantially reducing random errors in velocity. However, systematic errors continue to limit the ability of the flux-differencing technique used here to resolve local variations in mass balance. Nevertheless, significant local variations in mass balance are revealed, while, overall, Ice Streams D and E are in approximate equilibrium. An earlier estimate of the net mass balance for Ice Stream D is improved.
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Bindschadler, Robert, Patricia Vornberger, Donald Blankenship, Ted Scambos, and Robert Jacobel. "Surface velocity and mass balance of Ice Streams D and E, West Antarctica." Journal of Glaciology 42, no. 142 (1996): 461–75. http://dx.doi.org/10.1017/s0022143000003452.
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AbstractOver 75 000 surface-velocity measurements are extracted from sequential satellite imagery of Ice Streams D and E to reveal a complex pattern of flow not apparent from previous measurements. Horizontal and vertical strain rates, calculated from surface velocity, indicate that the bed experiences larger basal shear where the surface of these ice streams is rougher. Ten airborne-radar profiles and one surface-based radar profile of ice thickness make possible the calculation of mass balance for longitudinal sections of each ice stream. Improved data-collection methods increase data density, substantially reducing random errors in velocity. However, systematic errors continue to limit the ability of the flux-differencing technique used here to resolve local variations in mass balance. Nevertheless, significant local variations in mass balance are revealed, while, overall, Ice Streams D and E are in approximate equilibrium. An earlier estimate of the net mass balance for Ice Stream D is improved.
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Emerson, Steven, Paul Quay, and Patricia A. Wheeler. "Biological productivity determined from oxygen mass balance and incubation experiments." Deep Sea Research Part I: Oceanographic Research Papers 40, no. 11-12 (November 1993): 2351–58. http://dx.doi.org/10.1016/0967-0637(93)90109-g.
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Klug, Christoph, Erik Bollmann, Stephan Peter Galos, Lindsey Nicholson, Rainer Prinz, Lorenzo Rieg, Rudolf Sailer, Johann Stötter, and Georg Kaser. "Geodetic reanalysis of annual glaciological mass balances (2001–2011) of Hintereisferner, Austria." Cryosphere 12, no. 3 (March 6, 2018): 833–49. http://dx.doi.org/10.5194/tc-12-833-2018.
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Abstract. This study presents a reanalysis of the glaciologically obtained annual glacier mass balances at Hintereisferner, Ötztal Alps, Austria, for the period 2001–2011. The reanalysis is accomplished through a comparison with geodetically derived mass changes, using annual high-resolution airborne laser scanning (ALS). The grid-based adjustments for the method-inherent differences are discussed along with associated uncertainties and discrepancies of the two methods of mass balance measurements. A statistical comparison of the two datasets shows no significant difference for seven annual, as well as the cumulative, mass changes over the 10-year record. Yet, the statistical view hides significant differences in the mass balance years 2002/03 (glaciological minus geodetic records = +0.92 m w.e.), 2005/06 (+0.60 m w.e.), and 2006/07 (−0.45 m w.e.). We conclude that exceptional meteorological conditions can render the usual glaciological observational network inadequate. Furthermore, we consider that ALS data reliably reproduce the annual mass balance and can be seen as validation or calibration tools for the glaciological method.
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Callens, Denis, Nicolas Thonnard, Jan T. M. Lenaerts, Jan M. Van Wessem, Willem Jan Van de Berg, Kenichi Matsuoka, and Frank Pattyn. "Mass balance of the Sør Rondane glacial system, East Antarctica." Annals of Glaciology 56, no. 70 (2015): 63–69. http://dx.doi.org/10.3189/2015aog70a010.
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AbstractMass changes of polar ice sheets have an important societal impact, because they affect global sea level. Estimating the current mass budget of ice sheets is equivalent to determining the balance between surface mass gain through precipitation and outflow across the grounding line. For the Antarctic ice sheet, grounding line outflow is governed by oceanic processes and outlet glacier dynamics. In this study, we compute the mass budget of major outlet glaciers in the eastern Dronning Maud Land sector of the Antarctic ice sheet using the input/output method. Input is given by recent surface accumulation estimates (SMB) of the whole drainage basin. The outflow at the grounding line is determined from the radar data of a recent airborne survey and satellite-based velocities using a flow model of combined plug flow and simple shear. This approach is an improvement on previous studies, as the ice thickness is measured, rather than being estimated from hydrostatic equilibrium. In line with the general thickening of the ice sheet over this sector, we estimate the regional mass balance in this area at 3.15 ± 8.23 Gt a−1 according to the most recent SMB model results.
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Babonis, G. S., B. Csatho, and T. Schenk. "MASS BALANCE CHANGES AND ICE DYNAMICS OF GREENLAND AND ANTARCTIC ICE SHEETS FROM LASER ALTIMETRY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8 (June 23, 2016): 481–87. http://dx.doi.org/10.5194/isprs-archives-xli-b8-481-2016.
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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.
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Babonis, G. S., B. Csatho, and T. Schenk. "MASS BALANCE CHANGES AND ICE DYNAMICS OF GREENLAND AND ANTARCTIC ICE SHEETS FROM LASER ALTIMETRY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8 (June 23, 2016): 481–87. http://dx.doi.org/10.5194/isprsarchives-xli-b8-481-2016.
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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.
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De Marco, Jessica, Luca Carturan, Livia Piermattei, Sara Cucchiaro, Daniele Moro, Giancarlo Dalla Fontana, and Federico Cazorzi. "Minor Imbalance of the Lowermost Italian Glacier from 2006 to 2019." Water 12, no. 9 (September 8, 2020): 2503. http://dx.doi.org/10.3390/w12092503.
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The response of very small glaciers to climate changes is highly scattered and little known in comparison with larger ice bodies. In particular, small avalanche-fed and debris-covered glaciers lack mass balance series of sufficient length. In this paper we present 13 years of high-resolution observations over the Occidentale del Montasio Glacier, collected using Airborne Laser Scanning, Terrestrial Laser Scanning, and Structure from Motion Multi-View Stereo techniques for monitoring its geodetic mass balance and surface dynamics. The results have been analyzed jointly with meteorological variables, and compared to a sample of “reference” glaciers for the European Alps. From 2006 to 2019 the mass balance showed high interannual variability and an average rate much closer to zero than the average of the Alpine reference glaciers (−0.09 vs. −1.42 m water equivalent per year, respectively). This behavior can be explained by the high correlation between annual balance and solid precipitation, which displayed recent peaks. The air temperature is not significantly correlated with the mass balance, which is main controlled by avalanche activity, shadowing and debris cover. However, its rapid increase is progressively reducing the fraction of solid precipitation, and increasing the length of the ablation season.
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Krings, Thomas, Bruno Neininger, Konstantin Gerilowski, Sven Krautwurst, Michael Buchwitz, John P. Burrows, Carsten Lindemann, Thomas Ruhtz, Dirk Schüttemeyer, and Heinrich Bovensmann. "Airborne remote sensing and in situ measurements of atmospheric CO<sub>2</sub> to quantify point source emissions." Atmospheric Measurement Techniques 11, no. 2 (February 7, 2018): 721–39. http://dx.doi.org/10.5194/amt-11-721-2018.
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Abstract. Reliable techniques to infer greenhouse gas emission rates from localised sources require accurate measurement and inversion approaches. In this study airborne remote sensing observations of CO2 by the MAMAP instrument and airborne in situ measurements are used to infer emission estimates of carbon dioxide released from a cluster of coal-fired power plants. The study area is complex due to sources being located in close proximity and overlapping associated carbon dioxide plumes. For the analysis of in situ data, a mass balance approach is described and applied, whereas for the remote sensing observations an inverse Gaussian plume model is used in addition to a mass balance technique. A comparison between methods shows that results for all methods agree within 10 % or better with uncertainties of 10 to 30 % for cases in which in situ measurements were made for the complete vertical plume extent. The computed emissions for individual power plants are in agreement with results derived from emission factors and energy production data for the time of the overflight.
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Foroutan, Marzieh, Shawn J. Marshall, and Brian Menounos. "Automatic mapping and geomorphometry extraction technique for crevasses in geodetic mass-balance calculations at Haig Glacier, Canadian Rockies." Journal of Glaciology 65, no. 254 (September 16, 2019): 971–82. http://dx.doi.org/10.1017/jog.2019.71.
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AbstractFinely resolved geodetic data provide an opportunity to assess the extent and morphology of crevasses and their change over time. Crevasses have the potential to bias geodetic measurements of elevation and mass change unless they are properly accounted for. We developed a framework that automatically maps and extracts crevasse geometry and masks them where they interfere with surface mass-balance assessment. Our study examines airborne light detection and ranging digital elevation models (LiDAR DEMs) from Haig Glacier, which is experiencing a transient response in its crevassed upper regions as the glacier thins, using a self-organizing map algorithm. This method successfully extracts and characterizes ~1000 crevasses, with an overall accuracy of 94%. The resulting map provides insight into stress and flow conditions. The crevasse mask also enables refined geodetic estimates of summer mass balance. From differencing of September and April LiDAR DEMs, the raw LiDAR DEM gives a 9% overestimate in the magnitude of glacier thinning over the summer: −5.48 m compared with a mean elevation change of −5.02 m when crevasses are masked out. Without identification and removal of crevasses, the LiDAR-derived summer mass balance therefore has a negative bias relative to the glaciological surface mass balance.
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Bintanja, Richard. "The mass balance of a dry snow surface during a snowstorm." Annals of Glaciology 38 (2004): 79–83. http://dx.doi.org/10.3189/172756404781814898.
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AbstractThis paper focuses on the surface mass balance of a horizontally homogeneous snowfield, with emphasis on the effects of snowdrift sublimation. A one-dimensional model of the atmospheric boundary layer that includes snowdrift physics and thermodynamics is used. In sufficiently strong winds, snow particles are eroded from the surface. Once airborne, they are susceptible to sublimation. Averaged over longer time periods, the net erosive flux equals sublimation of snowdrift. However, model results show that there is no such balance in the course of a snowstorm event. They also indicate that snowdrift sublimation tends to enhance net erosion, but the increase occurs more slowly than the mass transfer by snowdrift sublimation, and the maximum is smaller. This difference in temporal behaviour influences the average erosion rate owing to non-linear interactions between snowdrift sublimation, drift density and erosion. Since the increase in relative humidity due to snowdrift diminishes surface sublimation, the average change in total ablation induced by snowdrift sublimation remains small. Observations made during snowdrift episodes in Antarctica agree qualitatively with some of the model results.
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Tadić, Jovan M., Anna M. Michalak, Laura Iraci, Velibor Ilić, Sébastien C. Biraud, Daniel R. Feldman, Thaopaul Bui, et al. "Elliptic Cylinder Airborne Sampling and Geostatistical Mass Balance Approach for Quantifying Local Greenhouse Gas Emissions." Environmental Science & Technology 51, no. 17 (August 8, 2017): 10012–21. http://dx.doi.org/10.1021/acs.est.7b03100.
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Fischer, A., H. Schneider, G. Merkel, and R. Sailer. "Comparison of direct and geodetic mass balances on an annual time scale." Cryosphere Discussions 5, no. 1 (February 14, 2011): 565–604. http://dx.doi.org/10.5194/tcd-5-565-2011.
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Abstract. Very accurate airborne laserscanning (ALS) elevation data was used to calculate the annual volume changes for Hintereisferner and Kesselwandferner in the Ötztal Alps, Austria for 2001/2002–2008/2009. The comparison of the altitude of 51 recently GPS surveyed ground control points showed that the accuracy of the ALS DEMs is better than 0.3 m. The geodetic mass balance was calculated from the volume change using detailed maps of the firn cover and applying corrections for the seasonal snow cover. The maximum snow height at the time of the elevation data flight was 0.5 m averaged over the glacier surface. The volume change data was compared to in situ mass balance data for the total area and at the stakes. For the total period of 8 yr, the difference between the geodetic and the direct mass balance is 2.398 m w.e. on Hintereisferner and 1.380 m w.e. on Kesselwandferner, corresponding to about two times the mean annual mass balance. The vertical ice flow velocity was measured and found to be on the same order of magnitude as the mass balance at KWF. This is an indicator that volume change data does not allow the calculation of ablation or accumulation rates without detailed measurements or models of the vertical ice flow velocity. Therefore, only direct mass balance data allow process studies or investigation of the climatic controls of the resulting mass changes.
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Geist, Thomas, Hallgeir Elvehøy, Miriam Jackson, and Johann Stötter. "Investigations on intra-annual elevation changes using multi-temporal airborne laser scanning data: case study Engabreen, Norway." Annals of Glaciology 42 (2005): 195–201. http://dx.doi.org/10.3189/172756405781812592.
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AbstractKey issues of glacier monitoring are changes in glacier geometry and glacier mass. As accurate direct measurements are costly and time-consuming, the use of various remote-sensing data for glacier monitoring is explored. One technology used and described here is airborne laser scanning. The method enables the derivation of high-quality digital elevation models (DEMs) with a vertical and horizontal accuracy in the sub-metre range. Between September 2001 and August 2002, three laser scanner data acquisition flights were carried out, covering the whole area of Engabreen, Norway, and corresponding well to the measurement dates for the mass-balance year 2001/02. The data quality of the DEMs is assessed (e.g. by comparing the values with a control area which has been surveyed independently or GPS ground profiles measured during the flights). For the whole glacier, surface elevation change and consequently volume change is calculated, quantified and compared with traditional mass-balance data for the same time interval. For the winter term, emergence/submergence velocity is determined from laser scanner data and snow-depth data and is compared with velocity measurements at stakes. The investigations reveal the high potential of airborne laser scanning for measuring the extent and the topography of glaciers as well as changes in geometry (Δarea, Δvolume).
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Qian, Xuewu, and Yanhua Zhu. "Self-Gradient Compensation of Full-Tensor Airborne Gravity Gradiometer." Sensors 19, no. 8 (April 25, 2019): 1950. http://dx.doi.org/10.3390/s19081950.
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In the process of airborne gravity gradiometry for the full-tensor airborne gravity gradiometer (FTAGG), the attitude of the carrier and the fuel mass will seriously affect the accuracy of gravity gradiometry. A self-gradient is the gravity gradient produced by the surrounding masses, and the surrounding masses include distribution mass for the carrier mass and fuel mass. In this paper, in order to improve the accuracy of airborne gravity gradiometry, a self-gradient compensation model is proposed for FTAGG. The self-gradient compensation model is a fuction of attitude for carrier and time, and it includes parameters ralated to the distribution mass for the carrier. The influence of carrier attitude and fuel mass on the self-gradient are simulated and analyzed. Simulation shows that the self-gradient tensor element Γ x x , Γ x y , Γ x z , Γ y z and Γ z z are greatly affected by the middle part of the carrier, and the self-gradient tensor element Γ y z is affected by the carrier’s fuel mass in three attitudes. Further simulation experiments show that the presented self-gradient compensation method is valid, and the error of the self-gradient compensation is within 0.1 Eu. Furthermore, this method can provide an important reference for improving the accuracy of aviation gravity gradiometry.
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Schuler, Thomas V., Regine Hock, Miriam Jackson, Hallgeir Elvehøy, Matthias Braun, Ian Brown, and Jon-Ove Hagen. "Distributed mass-balance and climate sensitivity modelling of Engabreen, Norway." Annals of Glaciology 42 (2005): 395–401. http://dx.doi.org/10.3189/172756405781812998.
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AbstractAssessing the impact of possible climate change on the water resources of glacierized areas requires a reliable model of the climate–glacier-mass-balance relationship. In this study, we simulate the mass-balance evolution of Engabreen, Norway, using a simple mass-balance model based on daily temperature and precipitation data from a nearby climate station. Ablation is calculated using a distributed temperature-index method including potential direct solar radiation, while accumulation is distributed linearly with elevation. The model was run for the period 1974/75–2001/02, for which annual mass-balance measurements and meteorological data are available. Parameter values were determined by a multi-criteria validation including point measurements of mass balance, mass-balance gradients and specific mass balance. The modelled results fit the observed mass balance well. Simple sensitivity experiments indicate a high sensitivity of the mass balance to temperature changes, as expected for maritime glaciers. The results suggest, further, that the mass balance of Engabreen is more sensitive to warming during summer than during winter, while precipitation changes affect almost exclusively the winter balance.
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Sold, Leo, Matthias Huss, Martin Hoelzle, Hubert Andereggen, Philip C. Joerg, and Michael Zemp. "Methodological approaches to infer end-of-winter snow distribution on alpine glaciers." Journal of Glaciology 59, no. 218 (2013): 1047–59. http://dx.doi.org/10.3189/2013jog13j015.
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AbstractSnow accumulation is an important component of the mass balance of alpine glaciers. To improve our understanding of the processes related to accumulation and their representation in state-of-the-art mass-balance models, extensive field measurements are required. We present measurements of snow accumulation distribution on Findelengletscher, Switzerland, for April 2010 using (1) in situ snow probings, (2) airborne ground-penetrating radar (GPR) and (3) differencing of two airborne light detection and ranging (lidar) digital elevation models (DEMs). Calculating high-resolution snow depth from DEM-differencing requires careful correction for vertical ice-flow velocity and densification in the accumulation area. All three methods reveal a general increase in snow depth with elevation, but also a significant small-scale spatial variability. Lidar-differencing and in situ snow probings show good agreement for the mean specific winter balance (0.72 and 0.78 m w.e., respectively). The lidar-derived distributed snow depth reveals significant zonal correlations with elevation, slope and curvature in a multiple linear regression model. Unlike lidar-differencing, GPR-derived snow depth is not affected by glacier dynamics or firn compaction, but to a smaller degree by snow density and liquid water content. It is thus a valuable independent data source for validation. The simultaneous availability of the three datasets facilitates the comparison of the methods and contributes to a better understanding of processes that govern winter accumulation distribution on alpine glaciers.
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van Pelt, W. J. J., J. Oerlemans, C. H. Reijmer, V. A. Pohjola, R. Pettersson, and J. H. van Angelen. "Simulating melt, runoff and refreezing on Nordenskiöldbreen, Svalbard, using a coupled snow and energy balance model." Cryosphere Discussions 6, no. 1 (January 20, 2012): 211–66. http://dx.doi.org/10.5194/tcd-6-211-2012.
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Abstract. A distributed energy balance model is coupled to a multi-layer snow model in order to study the mass balance evolution and the impact of refreezing on the mass budget of Nordenskiöldbreen, Svalbard. The model is forced with output of a regional climate model (RACMO) and meteorological data from Svalbard Airport. Extensive calibration and initialisation are performed to increase the model accuracy. For the period 1989–2010, we find a mean net mass balance of −0.39 m w.e. a−1. Refreezing contributes on average 0.27 m w.e. a−1 to the mass budget and is most pronounced in the accumulation zone. The simulated mass balance, radiative fluxes and subsurface profiles are validated against observations and are generally in good agreement. Climate sensitivity experiments reveal a non-linear, seasonally dependent response of the mass balance, refreezing and runoff to changes in temperature and precipitation. Output of the climate sensitivity experiments is used in combination with temperature and precipitation time-series to extend mass balance time-series in the past and the future to obtain estimates for the period 1912–2085. It is shown that including seasonality in climate change, with less pronounced summer warming, has a major impact on future mass balance and ELA estimates. Due to compensating effects, the contribution of refreezing hardly changes in a future climate.
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Fischer, A. "Comparison of direct and geodetic mass balances on a multi-annual time scale." Cryosphere 5, no. 1 (February 24, 2011): 107–24. http://dx.doi.org/10.5194/tc-5-107-2011.
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Abstract. The geodetic mass balances of six Austrian glaciers over 19 periods between 1953 and 2006 are compared to the direct mass balances over the same periods. For two glaciers, Hintereisferner and Kesselwandferner, case studies showing possible reasons for discrepancies between the geodetic and the direct mass balance are presented. The mean annual geodetic mass balance for all periods is −0.5 m w.e. a−1, the mean annual direct mass balance −0.4 m w.e. a−1. The mean cumulative difference is −0.6 m w.e., the minimum −7.3 m w.e., and the maximum 5.6 m w.e. The accuracy of geodetic mass balance may depend on the accuracy of the DEMs, which ranges from 2 m w.e. for photogrammetric data to 0.02 m w.e. for airborne laser scanning (LiDAR) data. Basal melt, seasonal snow cover, and density changes of the surface layer also contribute up to 0.7 m w.e. to the difference between the two methods over the investigated period of 10 yr. On Hintereisferner, the fraction of area covered by snow or firn has been changing within 1953–2006. The accumulation area is not identical with the firn area, and both are not coincident with areas of volume gain. Longer periods between the acquisition of the DEMs do not necessarily result in a higher accuracy of the geodetic mass balance. Trends in the difference between the direct and the geodetic data vary from glacier to glacier and can differ systematically for specific glaciers under specific types of climate forcing. Ultimately, geodetic and direct mass balance data are complementary, and great care must be taken when attempting to combine them.
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Tsiros, I. X. "A modeling analysis of factors influencing mass balance components of airborne deposited mercury in terrestrial landscapes." Journal of Environmental Science and Health, Part A 34, no. 10 (November 1999): 1979–2005. http://dx.doi.org/10.1080/10934529909376943.
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Jóhannesson, Tómas, Helgi Björnsson, Eyjólfur Magnússon, Sverrir Guðmundsson, Finnur Pálsson, Oddur Sigurðsson, Thorsteinn Thorsteinsson, and Etienne Berthier. "Ice-volume changes, bias estimation of mass-balance measurements and changes in subglacial lakes derived by lidar mapping of the surface of Icelandic glaciers." Annals of Glaciology 54, no. 63 (2013): 63–74. http://dx.doi.org/10.3189/2013aog63a422.
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AbstractIcelandic glaciers cover ∼11 000 km2 in area and store ∼3600 km3 of ice. Starting in 2008 during the International Polar Year, accurate digital elevation models (DEMs) of the glaciers are being produced with airborne lidar. More than 90% of the glaciers have been surveyed in this effort, including Vatnajökull, Hofsjökull, Myrdalsjökull, Drangajökull, Eyjafjallajökull and several smaller glaciers. The publicly available DEMs are useful for glaciological and geological research, including studies of ice-volume changes, estimation of bias in mass-balance measurements, studies of jökulhlaups and subglacial lakes formed by subglacial geothermal areas, and for mapping of crevasses. The lidar mapping includes a 500-1000 m wide ice-free buffer zone around the ice margins which contains many glacio-geomorphological features, and therefore the new DEMs have proved useful in geological investigations of proglacial areas. Comparison of the lidar DEMs with older maps confirms the rapid ongoing volume changes of the Icelandic ice caps which have been shown by mass-balance measurements since 1995/96. In some cases, ice-volume changes derived by comparing the lidar measurements with older DEMs are in good agreement with accumulated ice-volume changes derived from traditional mass-balance measurements, but in other cases such a comparison indicates substantial biases in the traditional mass-balance records.
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Das, Indrani, Regine Hock, Etienne Berthier, and Craig S. Lingle. "21st-century increase in glacier mass loss in the Wrangell Mountains, Alaska, USA, from airborne laser altimetry and satellite stereo imagery." Journal of Glaciology 60, no. 220 (2014): 283–93. http://dx.doi.org/10.3189/2014jog13j119.
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AbstractAlaskan glaciers are among the largest regional contributors to sea-level rise in the latter half of the 20th century. Earlier studies have documented extensive and accelerated ice wastage in most regions of Alaska. Here we study five decades of mass loss on high-elevation, land-terminating glaciers of the Wrangell Mountains (~ 4900 km2) in central Alaska based on airborne center-line laser altimetry data from 2000 and 2007, a digital elevation model (DEM) from ASTER and SPOT5, and US Geological Survey topographic maps from 1957. The regional mass-balance estimates derived from center-line laser altimetry profiles using two regional extrapolation techniques agree well with that from DEM differencing. Repeat altimetry measurements reveal accelerated mass loss over the Wrangell Mountains, with the regional mass-balance rate evolving from –0.07 ± 0.19 m w.e. a–1 during 1957–2000 to –0.24 ± 0.16 m w.e. a–1 during 2000–07. Nabesna, the largest glacier in this region (˜1056 km2), lost mass four times faster during 2000–07 than during 1957–2000. Although accelerated, the mass change over this region is slower than in other glacierized regions of Alaska, particularly those with tidewater glaciers. Together, our laser altimetry and satellite DEM analyses demonstrate increased wastage of these glaciers during the last 50 years.
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Albrecht, Olaf, Peter Jansson, and Heinz Blatter. "Modelling glacier response to measured mass-balance forcing." Annals of Glaciology 31 (2000): 91–96. http://dx.doi.org/10.3189/172756400781819996.
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AbstractMeasurements of summer and winter mass balances have been carried out over the past 53 years on Storglaciären, northern Sweden. Repeated surveys of the glacier have resulted in several maps of surface topography as well as a map of the bed topography A new time-dependent ice flow model allows us to compare the observed surface evolution of the glacier with that computed by the model using measured mass-balance maps as input. The computed volume change compares well with the measured change: the model replicates the distribution of surface elevation to within ±10 m over 30 years of integration. On the model side, these deviations can be attributed to the low-resolution discretization of the model domain as well as to the limited accuracy of the ice rheology and omitted basal sliding. On the other hand, the uncertainties of the topography and mass-balance maps match the model uncertainties. In this sense, the experiments are a validation of both model and observations.
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Farías-Barahona, David, Álvaro Ayala, Claudio Bravo, Sebastián Vivero, Thorsten Seehaus, Saurabh Vijay, Marius Schaefer, Franco Buglio, Gino Casassa, and Matthias H. Braun. "60 Years of Glacier Elevation and Mass Changes in the Maipo River Basin, Central Andes of Chile." Remote Sensing 12, no. 10 (May 21, 2020): 1658. http://dx.doi.org/10.3390/rs12101658.
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Glaciers in the central Andes of Chile are fundamental freshwater sources for ecosystems and communities. Overall, glaciers in this region have shown continuous recession and down-wasting, but long-term glacier mass balance studies providing precise estimates of these changes are scarce. Here, we present the first long-term (1955–2013/2015), region-specific glacier elevation and mass change estimates for the Maipo River Basin, from which the densely populated metropolitan region of Chile obtains most of its freshwater supply. We calculated glacier elevation and mass changes using historical topographic maps, Shuttle Radar Topography Mission (SRTM), TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X), and airborne Light Detection and Ranging (LiDAR) digital elevation models. The results indicated a mean regional glacier mass balance of −0.12 ± 0.06 m w.e.a−1, with a total mass loss of 2.43 ± 0.26 Gt for the Maipo River Basin between 1955–2013. The most negative glacier mass balance was the Olivares sub-basin, with a mean value of −0.29 ± 0.07 m w.e.a−1. We observed spatially heterogeneous glacier elevation and mass changes between 1955 and 2000, and more negative values between 2000 and 2013, with an acceleration in ice thinning rates starting in 2010, which coincides with the severe drought. Our results provide key information to improve glaciological and hydrological projections in a region where water resources are under pressure.
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Moholdt, G., J. O. Hagen, T. Eiken, and T. V. Schuler. "Geometric changes and mass balance of the Austfonna ice cap, Svalbard." Cryosphere Discussions 3, no. 3 (October 13, 2009): 857–93. http://dx.doi.org/10.5194/tcd-3-857-2009.
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Abstract. The dynamics and mass balance regime of the Austfonna ice cap, the largest glacier on Svalbard, deviate significantly from most other glaciers in the region and is not fully understood. We have compared ICESat laser altimetry, airborne laser altimetry, GNSS surface profiles and radio echo-sounding data to estimate elevation change rates for the periods 1983–2007 and 2002–2008. The data sets indicate a pronounced interior thickening of up to 0.5 m y−1, at the same time as the margins are thinning at a rate of 1–3 m y−1. The southern basins are thickening at a higher rate than the northern basins due to a higher accumulation rate. The overall volume change in the 2002–2008 period is estimated to be −1.3±0.5 km3 w.e. y−1 (or −0.16±0.06 m w.e. y−1) where the entire net loss is due to a rapid retreat of the calving fronts. Since most of the marine ice loss occurs below sea level, Austfonna's current contribution to sea level change is close to zero. The geodetic results are compared to in-situ mass balance measurements which indicate that the 2004–2008 surface net mass balance has been slightly positive (0.05 m w.e. y−1) though with large annual variations. Similarities between local net mass balances and local elevation changes indicate that most of the ice cap is dormant and not in dynamic equilibrium with the current climate. More knowledge is needed about century-scale dynamic processes in order to predict the future evolution of Austfonna based on climate scenarios.
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Moholdt, G., J. O. Hagen, T. Eiken, and T. V. Schuler. "Geometric changes and mass balance of the Austfonna ice cap, Svalbard." Cryosphere 4, no. 1 (January 19, 2010): 21–34. http://dx.doi.org/10.5194/tc-4-21-2010.
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Abstract. The dynamics and mass balance regime of the Austfonna ice cap, the largest glacier on Svalbard, deviates significantly from most other glaciers in the region and is not fully understood. We have compared ICESat laser altimetry, airborne laser altimetry, GNSS surface profiles and radio echo-sounding data to estimate elevation change rates for the periods 1983–2007 and 2002–2008. The data sets indicate a pronounced interior thickening of up to 0.5 m y−1, at the same time as the margins are thinning at a rate of 1–3 m y−1. The southern basins are thickening at a higher rate than the northern basins due to a higher accumulation rate. The overall volume change in the 2002–2008 period is estimated to be −1.3±0.5 km3 w.e. y−1 (or −0.16±0.06 m w.e. y−1) where the entire net loss is due to a rapid retreat of the calving fronts. Since most of the marine ice loss occurs below sea level, Austfonna's current contribution to sea level change is close to zero. The geodetic results are compared to in-situ mass balance measurements which indicate that the 2004–2008 surface net mass balance has been slightly positive (0.05 m w.e. y−1) though with large annual variations. Similarities between local net mass balances and local elevation changes indicate that most of the ice cap is slow-moving and not in dynamic equilibrium with the current climate. More knowledge is needed about century-scale dynamic processes in order to predict the future evolution of Austfonna based on climate scenarios.
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König, Max, Jan-Gunnar Winther, Niels Tvis Knudsen, and Tore Guneriussen. "Firn-line detection on Austre Okstindbreen, Norway, with airborne multipolarization SAR." Journal of Glaciology 47, no. 157 (2001): 251–57. http://dx.doi.org/10.3189/172756501781832241.
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AbstractWe examine the ability of synthetic aperture radar (SAR) to detect the equilibrium line on the glacier Austre Okstindbreen, Norway, using multipolarization SAR images in C- and L-band acquired with the Electromagnetic Institute of the Technical University of Denmark’s airborne EMISAR sensor during the European Multisensor Airborne Campaign EMAC ’95. The late-summer snowline, approximating the equilibrium line, cannot be seen on the SAR images. Instead, photographs from Austre Okstind-breen show that a distinct boundary visible on the C-band SAR images corresponds to the firn line created by old snow from many previous years. This is better seen on the cross-polarized SAR images (HV and VH), which in general reveal more detail than the HH- and VV-polarized images. We model the stratigraphy from net balance and glacier velocity data to calculate the firn-line altitude (FLA). Modelled FLA and the observed boundary are separated by 50 m in elevation, but considering errors during co-registration and modelling we conclude that the observed boundary on Austre Okstindbreen is the firn line. Monitoring FLA rather than equilibrium-line altitude (ELA) for mass-balance studies with remote sensing is therefore suggested.
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Fujii, Yusaku, Koichi Maru, Kazuhito Shimada, Tao Jin, and William Thornton. "Space Balance and Space Scale: Mass Measurement Devices (MMDs)." Applied Mechanics and Materials 36 (October 2010): 31–40. http://dx.doi.org/10.4028/www.scientific.net/amm.36.31.
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In this paper, mass measurement devices (MMDs) developing by the authors for use in the International Space Station (ISS) are reviewed. First, Space Balance, which is a small mass measurement device (SMMD), is reviewed. In Space Balance, the momentum conservation between two objects, the subject mass and the reference mass, are compared. Then Space Scale, which is a body mass measurement device (BMMD), is reviewed. In Space Scale, a human subject is pulled using rubber string. Force is measured using a force transducer and acceleration is measured using optical interferometer. Both Space Balance and Space Scale have shown high accuracies in the ground experiments.
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Koenig, L. S., A. Ivanoff, P. M. Alexander, J. A. MacGregor, X. Fettweis, B. Panzer, J. D. Paden, et al. "Annual Greenland accumulation rates (2009–2012) from airborne Snow Radar." Cryosphere Discussions 9, no. 6 (December 10, 2015): 6697–731. http://dx.doi.org/10.5194/tcd-9-6697-2015.
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Abstract. Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet (GrIS) through increasing surface melt, emphasizing the need to closely monitor surface mass balance (SMB) in order to improve sea-level rise predictions. Here, we quantify accumulation rates, the largest component of GrIS SMB, at a higher spatial resolution than currently available, using Snow Radar stratigraphy. We use a semi-automated method to derive annual-net accumulation rates from airborne Snow Radar data collected by NASA's Operation IceBridge from 2009 to 2012. An initial comparison of the accumulation rates from the Snow Radar and the outputs of a regional climate model (MAR) shows that, in general, the radar-derived accumulation matches closely with MAR in the interior of the ice sheet but MAR estimates are high over the southeast GrIS. Comparing the radar-derived accumulation with contemporaneous ice cores reveals that the radar captures the annual and long-term mean. The radar-derived accumulation rates resolve large-scale patterns across the GrIS with uncertainties of up to 11 %, attributed mostly to uncertainty in the snow/firn density profile.
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Ligtenberg, S. R. M., B. Medley, M. R. Van Den Broeke, and P. Kuipers Munneke. "Antarctic firn compaction rates from repeat-track airborne radar data: II. Firn model evaluation." Annals of Glaciology 56, no. 70 (2015): 167–74. http://dx.doi.org/10.3189/2015aog70a204.
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AbstractThe thickness and density of the Antarctic firn layer vary considerably in time and space, thereby contributing to ice-sheet volume and mass changes. Distinguishing between these mass and volume changes is important for ice-sheet mass-balance studies. Evolution of firn layer depth and density is often modeled, because direct measurements are scarce. Here we directly compare modeled firn compaction rates with observed rates obtained from repeat-track airborne radar data over a 2 year interval (2009–11) in West Antarctica. Spatially, the observed compaction rates exhibit significant variability, but when averaged to scales comparable to the model resolution (20–50 km), the measurements and model results qualitatively agree. A colder and drier period preceding the 2009 survey led to lower compaction rates during the 2009–10 interval, when compared to 2010–11, which is partly captured by the firn model. Spatially, higher compaction rates are observed and modeled in warmer regions with higher accumulation.
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Lundberg, Karl-Ola. "An Alternative Method for Measurement of Airborne Sound Insulation." Building Acoustics 8, no. 1 (March 2001): 57–74. http://dx.doi.org/10.1260/1351010011501731.
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A method for determination of the transmission coefficient from Complex Modulation Transfer Functions CMTF:s based on measured impulse-responses is shown. In the method a separate measurement of the equivalent sound absorption area is not needed in contrast to in the standardised measurement. By averaging over a number of estimates of the impulse-response the influence of background noise can be reduced substantially, implying that low-power sources can be used. A model for the power balance in the receiving room with time-varying power is considered. In the model the quotient of the receiving room intensity and the source room intensity has one pole, which is proportional to the equivalent sound absorption area in the receiving room, and a gain, proportional to the transmission coefficient. In the physical system the power can be time-varied by letting the system excitation signal consist of random noise modulated with a deterministic time-varying function. However, since the ensemble average of the squared response is proportional to the squared impulse-response convolved with the squared modulating function, random excitation is avoided and replaced by impulse-response measurements. The quotient of intensities in the model is in the physical system a quotient of CMTF:s. Experiments are carried out in an airborne sound insulation laboratory. For comparison, standardised measurements are also carried out. It is found that the presented method gives as result comparatively small transmission coefficients, though the relative differences are small. By refining the power balance model by introducing an energy propagation time delay, and selecting an appropriate delay, the differences were diminished.
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Johnson, Austin J., Christopher F. Larsen, Nathaniel Murphy, Anthony A. Arendt, and S. Lee Zirnheld. "Mass balance in the Glacier Bay area of Alaska, USA, and British Columbia, Canada, 1995–2011, using airborne laser altimetry." Journal of Glaciology 59, no. 216 (2013): 632–48. http://dx.doi.org/10.3189/2013jog12j101.
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AbstractThe Glacier Bay region of southeast Alaska, USA, and British Columbia, Canada, has undergone major glacier retreat since the Little Ice Age (LIA). We used airborne laser altimetry elevation data acquired between 1995 and 2011 to estimate the mass loss of the Glacier Bay region over four time periods (1995–2000, 2000–05, 2005–09, 2009–11). For each glacier, we extrapolated from center-line profiles to the entire glacier to estimate glacier-wide mass balance, and then averaged these results over the entire region using three difference methods (normalized elevation, area-weighted method and simple average). We found that there was large interannual variability of the mass loss since 1995 compared with the long-term (post-LIA) average. For the full period (1995–2011) the average mass loss was 3.93 ± 0.89 Gt a−1 (0.6 ± 0.1 m w.e. a−1), compared with 17.8 Gt a−1 for the post-LIA (1770–1948) rate. Our mass loss rate is consistent with GRACE gravity signal changes for the 2003–10 period. Our results also show that there is a lower bias due to center-line profiling than was previously found by a digital elevation model difference method.
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Jenkins, A., and C. S. M. Doake. "Basal Mass Balance Along a Flow Line on Ronne Ice Shelf, Antarctica (Abstract)." Annals of Glaciology 11 (1988): 201. http://dx.doi.org/10.3189/s0260305500006583.
Full textAbstract:
Recent glaciological work on Ronne Ice Shelf has focused on an assumed flow line which extends from Rutford Ice Stream grounding line to the ice front. Results from doppler satellite surveying and radio echo-sounding are used in kinematic calculations to determine the basal mass balance, assuming the flow line to be in a steady state. Models suggest that basal melting dominates over most of the flow line and is most pronounced at the extremities. In the region within 300 km of the grounding line and over the final 45 km before the ice front, at least 1 m/a on average must melt away to maintain the observed velocity and thickness profile. More gentle melting occurs over about half the remaining distance, but in a region between 130 and 300 km in from the ice front, basal freezing must occur at an average rate of about 0.1 m/a to maintain a steady state. The existence of a thin layer of saline ice underlying the ice shelf, which persists for a further 80 km down-stream before being melted away entirely, is consistent with the weak returns observed during both airborne and ground-based radio echo-sounding in this region.
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Jenkins, A., and C. S. M. Doake. "Basal Mass Balance Along a Flow Line on Ronne Ice Shelf, Antarctica (Abstract)." Annals of Glaciology 11 (1988): 201. http://dx.doi.org/10.1017/s0260305500006583.
Full textAbstract:
Recent glaciological work on Ronne Ice Shelf has focused on an assumed flow line which extends from Rutford Ice Stream grounding line to the ice front. Results from doppler satellite surveying and radio echo-sounding are used in kinematic calculations to determine the basal mass balance, assuming the flow line to be in a steady state. Models suggest that basal melting dominates over most of the flow line and is most pronounced at the extremities. In the region within 300 km of the grounding line and over the final 45 km before the ice front, at least 1 m/a on average must melt away to maintain the observed velocity and thickness profile. More gentle melting occurs over about half the remaining distance, but in a region between 130 and 300 km in from the ice front, basal freezing must occur at an average rate of about 0.1 m/a to maintain a steady state. The existence of a thin layer of saline ice underlying the ice shelf, which persists for a further 80 km down-stream before being melted away entirely, is consistent with the weak returns observed during both airborne and ground-based radio echo-sounding in this region.
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Lindbäck, K., R. Pettersson, S. H. Doyle, C. Helanow, P. Jansson, S. Savstrup Kristensen, L. Stenseng, R. Forsberg, and A. L. Hubbard. "High-resolution ice thickness and bed topography of a land-terminating section of the Greenland Ice Sheet." Earth System Science Data Discussions 7, no. 1 (March 26, 2014): 129–48. http://dx.doi.org/10.5194/essdd-7-129-2014.
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Abstract. We present ice thickness and bed topography maps with high spatial resolution (250 to 500 m) of a and-terminating section of the Greenland Ice Sheet derived from combined ground-based and airborne radar surveys. The data have a total area of ~12000 km2 and cover the whole ablation area of the outlet glaciers of Isunnguata Sermia, Russell, Leverett, Ørkendalen and Isorlersuup up to the long-term mass balance equilibrium line altitude at ~1600 m above sea level. The bed topography shows highly variable subglacial trough systems, and the trough of the Isunnguata Sermia Glacier is over-deepened and reaches an elevation of several hundreds of meters below sea level. The ice surface is smooth and only reflects the bedrock topography in a subtle way, resulting in a highly variable ice thickness. The southern part of our study area consists of higher bed elevations compared to the northern part. The covered area is one of the most studied regions of the Greenland Ice Sheet with studies of mass balance, dynamics, and supraglacial lakes, and our combined dataset can be valuable for detailed studies of ice sheet dynamics and hydrology. The compiled datasets of ground-based and airborne radar surveys are accessible for reviewers (password protected) at doi.pangaea.de/10.1594/pangaea.830314 and will be freely available in the final revised paper.
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Kuhlmann, Gerrit, Ka Lok Chan, Sebastian Donner, Ying Zhu, Marc Schwaerzel, Steffen Dörner, Jia Chen, et al. "Mapping the spatial distribution of NO<sub>2</sub> with in situ and remote sensing instruments during the Munich NO<sub>2</sub> imaging campaign." Atmospheric Measurement Techniques 15, no. 6 (March 21, 2022): 1609–29. http://dx.doi.org/10.5194/amt-15-1609-2022.
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Abstract. We present results from the Munich Nitrogen dioxide (NO2) Imaging Campaign (MuNIC), where NO2 near-surface concentrations (NSCs) and vertical column densities (VCDs) were measured with stationary, mobile, and airborne in situ and remote sensing instruments in Munich, Germany. The most intensive day of the campaign was 7 July 2016, when the NO2 VCD field was mapped with the Airborne Prism Experiment (APEX) imaging spectrometer. The spatial distribution of APEX VCDs was rather smooth, with a horizontal gradient between lower values upwind and higher values downwind of the city center. The NO2 map had no pronounced source signatures except for the plumes of two combined heat and power (CHP) plants. The APEX VCDs have a fair correlation with mobile multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations from two vehicles conducted on the same afternoon (r=0.55). In contrast to the VCDs, mobile NSC measurements revealed high spatial and temporal variability along the roads, with the highest values in congested areas and tunnels. The NOx emissions of the two CHP plants were estimated from the APEX observations using a mass-balance approach. The NOx emission estimates are consistent with CO2 emissions determined from two ground-based Fourier transform infrared (FTIR) instruments operated near one CHP plant. The estimates are higher than the reported emissions but are probably overestimated because the uncertainties are large, as conditions were unstable and convective with low and highly variable wind speeds. Under such conditions, the application of mass-balance approaches is problematic because they assume steady-state conditions. We conclude that airborne imaging spectrometers are well suited for mapping the spatial distribution of NO2 VCDs over large areas. The emission plumes of point sources can be detected in the APEX observations, but accurate flow fields are essential for estimating emissions with sufficient accuracy. The application of airborne imaging spectrometers for studying NSCs is less straightforward and requires us to account for the non-trivial relationship between VCDs and NSCs.
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Hastie, Alan R., and J. Godfrey Fitton. "Eoarchaean tectonics: New constraints from high pressure-temperature experiments and mass balance modelling." Precambrian Research 325 (June 2019): 20–38. http://dx.doi.org/10.1016/j.precamres.2019.02.006.
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Krepper, Eckhard, Matthias Beyer, Dirk Lucas, and Martin Schmidtke. "A population balance approach considering heat and mass transfer—Experiments and CFD simulations." Nuclear Engineering and Design 241, no. 8 (August 2011): 2889–97. http://dx.doi.org/10.1016/j.nucengdes.2011.05.003.
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