DOCSLIB.ORG

© Cambridge University Press Cambridge

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
© Cambridge University Press Cambridge Cambridge University Press 978-0-521-80620-6 - Creep and Fracture of Ice Erland M. Schulson and Paul Duval Index More information Index 100-year wave force, 336 friction and fracture, 289, 376 60° dislocations, 17, 82, 88 indentation failure, 345 microstructure, 45, 70, 237, 255, 273 abrasion, 337 multiscale fracture and frictional accommodation processes of basal slip, 165 sliding, 386 acoustic emission, 78, 90, 108 nested envelopes, 377 across-column cleavage cracks, 278 pressure–area relationship, 349, 352 across-column confinement, 282 S2 growth texture, 246, 273 across-column cracks, 282, 306, SHEBA faults, 371 across-column loading, 275 SHEBA stress states, 377 across-column strength, 246, 249, 275 Arctic Ocean, 1, 45, 190, 361 activation energy, 71, 84, 95, 111, 118, 131 aspect ratio, 344 activation volume, 114, 182 atmospheric ice, 219, 221, 241, 243 activity of pyramidal slip systems, 158 atmospheric icing, 31 activity of slip systems, 168 atmospheric impurities, 113 adiabatic heating, 291, 348 atomic packing factor, 9 adiabatic softening, 291 audible report, 240 affine self-consistent model, 160 avalanches, 206 air bubbles, 38 air-hydrate crystals, 37 bands, 89 albedo, 363 basal activity, 162 aligned first-year sea ice, 246 basal dislocations, 77 along-column confinement, 282 basal planes, 214, along-column confining stress, 282, basal screw dislocations, 77, 87 along-column strength, 244, 275 basal shear bands, 163 ammonia dihydrate, 181 basal slip, 18, 77, 127, 228 ammonia–water system, 186 basal slip lines, 77 amorphous forms of ice, 5 bend strength, 213, 224 Andrade creep, 108 bend test, 213 Andrade law, 104, 107 Bernal–Fowler ice rules, 9 anisotropic ice, 129, 153, 154, 156, 172, biaxial compressive strength, 270 apparent activation energy, 342 biaxial loading, 270, 274 apparent contact area, 349 paths, 274 apparent fracture toughness, 204, 341 Bjerrum defects, 15, 82, 88, applied stress tensor, 280 blowout, 297 arctic and antarctic sea ice blue zone, 347, 348 aligned first-year sea ice, 246 boundary diffusion, 126 brine-drainage channels, 43, 223 Brazil test, 213, brine pockets, 43, 62, 217, 223, brine drainage channels, 43, 224, 231 224, 249 ductile–brittle transition, 118, 119 brine pockets, 43, 62, 217, 224, 231 failure envelope, 275, 278, 376 brittle behavior, 240 391 © Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-80620-6 - Creep and Fracture of Ice Erland M. Schulson and Paul Duval Index More information 392 Index brittle compressive failure, 237 columnar-shaped grains, 31, 41 brittle compressive strength of confined ice comb cracks, 266, 296, 297, 366 biaxial loading, 270, 274 mechanism, 300, biaxial loading paths, 274 compact tensile specimens, 198 comb-crack mechanism, 300, compliance, 157 confinement strengthening, 276 matrix, 60 confinement weakening, 276, 280 compliant brush platens, 238 Coulombic faults, 272, 278, 282, 314 compressibility, 55 failure envelope, 275, 278, 376 compressive shear faults, 236, 372 failure surfaces, 286 compressive strength fracture and friction, 289 compliant brush platens, 238 plastic faults, 272, 282, 292, 308, 314 failure process, 251 post-terminal failure, 267 length-to-diameter ratio, 238 pressure-cell method, 267 loading platens, 238 proportional loading, 267 longitudinal split, 251 triaxial test, 267 multiple splitting, 240 true triaxial loading, 268 parallelism of ends, 238 wing cracks and comb cracks, 294 specimen shape, 238 brittle failure modes, 342 stiffness of loading frame, 237 blue zone, 347, 356 vs. cyclic loading, 249 continuous, 337 vs. damage, 249 high-pressure zone, 348, 356 vs. grain size, 247 local loads, 349 vs. growth texture, 246 non-simultaneous failure, 349 vs. porosity/salinity, 247 pressure–area curve, 351 vs. size and boundary conditions, 250 strain-rate softening, 240, 243, 338 vs. strain rate, 243 transition strain rate, 239, 309, 331 vs. temperature, 245 transition velocity, 341 wing-crack mechanics, 261 brittle failure surface, 288 concentric cracks, 356 brittle fracture mode confined single crystals, 237 Coulombic faulting, 282, 348 confinement, 242, 266, 328, 344, 375 intergranular, 320 strengthening, 276 spalling, 278, 304, 343 weakening, 276, 280 splitting, 327 confining pressure, 116, 267, 269 transgranular, 216 conjugate fracture, 365 brittle-like failure mode conjugate sets, 272 plastic faulting, 292, 308, 348 constitutional super-cooling, 43 brittle-to-ductile transition, 226,242, 320, 337, 386 constriction of partial dislocations, 89 bubbly ice, 30, 37 contact area, 350 buckling, 306 contact zone, 266, 292, 336, 347, 355 stress, 369 continuous indentation, 337 bulk modulus, 58 continuous recrystallization, 128 Burgers’ vector b, 16, 89 convective flow, 186 Coulombic faults, 272, 278, 282, 314 c-axis alignment, 45 shear fault, 276, 282, 303, 373 calving of icebergs, 1, 212 Coulombic material, 237 cellular material, 207 Coulomb’s failure criterion, 259, 310 ceramics, 247 covalent bonds, 7, 188 chemical compounds, 34 cracked/damaged polycrystals, 64 circumferential cracking, 343 cracks ,68 circumferentially notched tensile bars, 198 cleavage, 216 cleavage, 214, 216 comb, 266, 294, 296, 297, 366 climb, 16 critical crack, 229 basal dislocations, 122 density, 249 dislocations, 125 extension force, 192 CO2 hydrate, 180 frictional sliding, 68, 237, 247, 261, 278, 282, 289, cohesion, 289, 290, 311 302, 375, 376 cohesive strength, 228, 260, 311, growth, 40, 196 coincident site lattice, 22 horsetail, 299 collective dislocation motion, 91, 94 interaction, 258 columnar ice, 162, 219, 246, 273 intergranular, 320 © Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-80620-6 - Creep and Fracture of Ice Erland M. Schulson and Paul Duval Index More information Index 393 cracks (cont.) ice Ih, 5 micro-plates, 297, 300 radial isotropy, 9, 14 most dangerous flaw, 352 cyclic bending tests, 250 nucleation, 39, 212, 229 cyclic hardening, 250 control, 229 cyclic loading, 83, 205, 249 parent, 252, primary, 251, 294 D-type Bjerrum defect, 11 propagation, 228, 231 damage, 66, 68, 203, 222, 249, 262, 266, 294, control, 228 328, 347 secondary, 251, 255, 266, 282, 296, 324, 366 theory, 64 splay, 299 threshold, 249 systems, 194, 195 damage-dependent elastic stiffness constants, 66 tip creep, 197 debris-laden ice, 113, tip stress state, 193 decohesions, 231 transgranular, 216 deformation gradients, 79, 96, 155 velocities, 231 deformation matrix, 66 wing, 252, 258, 294, 361, 366, 372 deformation textures, 139 crater dimensions, 356 deformation twins, 22 cratering, 355 delayed elastic strain, 103 creep densification, 37, 160 activation energy, 71, 84, 95, 111, 118, 131 density, 8, 207 Andrade creep, 109 destabilization, 297, 304 behavior at low stresses, 109 deviatoric stresses, 109 diffusion creep, 103, 125, 126 diamond anvil cell, 182 effect of confining pressure, 114 diamond-shaped patterns, 362 effect of grain size, 107, 112 differential stress, 270 effect of liquid phase, 127 diffusion effect of particles and impurities, 113 dislocation climb, 90, 95, 125 glide-controlled mechanism, 124 self-diffusion, 70, 123 Harper–Dorn creep, 125, volume diffusion coefficient, 122 melt-free pure ice, 111 diffusion of acids, 72 primary creep, 103, 104, 161 diffusion coefficient, 70, 71 rate-controlling processes, 95, 122, 124 diffusion creep, 103, 125, 126 recovery creep, 115 diffusion of gases, 70, 72 secondary creep, 103, 109, 111, 112, 113, dimensional analysis, 352, 356 122, 311 directional viscosity, 154 stress exponent, 109, 116, 128, 160, 179, 187 direct tensile test, 214 superplastic flow, 112, 125 dirty ice, 330 tertiary creep, 103, 115, 129 dislocation motion creep damage, 250 avalanches, 78, 90, 92, 94, 107, 108, 230 creep relaxation, 258 basal slip, 18, 77, 127, 228 creep zone, 324 climb, 90, 95 crevasses, 212, collective motion, 91, 94 critical cracks, 229 cross-slip, 16, 18, 77, 89, 95, 123 critical flaw, 231 dislocation mobility, 82, 87, critical grain size, 221, 222, dislocation velocity, 87, 88 critical loading rate, 197, glide-controlled mechanism, 124 critical nucleus, 39 mobile dislocations, 78, 82, 95 critical size, 228 Orowan equation, 92, 124 critical strain rate, 320 prismatic slip, 161, 243 critical stress for crack propagation, 192 dislocations , 12, 70, 73 cross-slip, 16, 18, 77, 89, 95, 123 60° dislocations, 17, 82, 88 crushing, 343, 345 avalanches, 78, 90, 92, 94, 107, 108, 230 force, 354 basal dislocations, 77 crystalline forms of ice, 5 basal screw dislocations, 77, 87 crystals, 125 climb, 90, 95 growth, 40 density, 15, 21 plasticity, 362 dissociation, 18, 89 structure of ice Ih, 6 edge, 13, 86, 88, 164 crystal structure excess dislocations, 95, 143 ice Ic, 5 interstitial prismatic loop, 14 © Cambridge University Press www.cambridge.org Cambridge University Press 978-0-521-80620-6 - Creep and Fracture of Ice Erland M. Schulson and Paul Duval Index More information 394 Index dislocations (cont.) effect of temperature, 111 jogs, 123 effective shear stress, 260, 266 kinetics, 213 elastic anisotropy, 58, 64 line energy, 16 elastic buckling, 297, 369 line (strain) energy, 16 elastic compliance constants, 52, 54 loops, 71 elastic constants, 66 mixed, 14 elastic energy, 137, 191 mobility, 82, 87, elastic limit, 323 multiplication, 24, 79, 89, 94, 96 elastic mismatch, 229, non-basal edge dislocations, 20, 77 elastic moduli, 54 partial dislocations, 18, 22, 89 elastic stiffness constants, 52 pile-ups, 229, elastically isotropic, 58 prismatic loop, 14, 18 elasto-viscoplastic, 160
Load more

Recommended publications
  • Proton Ordering and Reactivity of Ice
    1 Proton ordering and reactivity of ice Zamaan Raza Department of Chemistry University College London Thesis submitted for the degree of Doctor of Philosophy September 2012 2 I, Zamaan Raza, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 3 For Chryselle, without whom I would never have made it this far. 4 I would like to thank my supervisors, Dr Ben Slater and Prof Angelos Michaelides for their patient guidance and help, particularly in light of the fact that I was woefully unprepared when I started. I would also like to express my gratitude to Dr Florian Schiffmann for his indispens- able advice on CP2K and quantum chemistry, Dr Alexei Sokol for various discussions on quantum mechanics, Dr Dario Alfé for his incredibly expensive DMC calculations, Drs Jiri Klimeš and Erlend Davidson for advice on VASP, Matt Watkins for help with CP2K, Christoph Salzmann for discussions on ice, Dr Stefan Bromley for allowing me to work with him in Barcelona and Drs Aron Walsh, Stephen Shevlin, Matthew Farrow and David Scanlon for general help, advice and tolerance. Thanks and also apologies to Stephen Cox, with whom I have collaborated, but have been unable to contribute as much as I should have. Doing a PhD is an isolating experience (more so in the Kathleen Lonsdale building), so I would like to thank my fellow students and friends for making it tolerable: Richard, Tiffany, and Chryselle. Finally, I would like to acknowledge UCL for my funding via a DTA and computing time on Legion, the Materials Chemistry Consortium (MCC) for computing time on HECToR and HPC-Europa2 for the opportunity to work in Barcelona.
    [Show full text]
  • Ice Ic” Werner F
    Extent and relevance of stacking disorder in “ice Ic” Werner F. Kuhsa,1, Christian Sippela,b, Andrzej Falentya, and Thomas C. Hansenb aGeoZentrumGöttingen Abteilung Kristallographie (GZG Abt. Kristallographie), Universität Göttingen, 37077 Göttingen, Germany; and bInstitut Laue-Langevin, 38000 Grenoble, France Edited by Russell J. Hemley, Carnegie Institution of Washington, Washington, DC, and approved November 15, 2012 (received for review June 16, 2012) “ ” “ ” A solid water phase commonly known as cubic ice or ice Ic is perfectly cubic ice Ic, as manifested in the diffraction pattern, in frequently encountered in various transitions between the solid, terms of stacking faults. Other authors took up the idea and liquid, and gaseous phases of the water substance. It may form, attempted to quantify the stacking disorder (7, 8). The most e.g., by water freezing or vapor deposition in the Earth’s atmo- general approach to stacking disorder so far has been proposed by sphere or in extraterrestrial environments, and plays a central role Hansen et al. (9, 10), who defined hexagonal (H) and cubic in various cryopreservation techniques; its formation is observed stacking (K) and considered interactions beyond next-nearest over a wide temperature range from about 120 K up to the melt- H-orK sequences. We shall discuss which interaction range ing point of ice. There was multiple and compelling evidence in the needs to be considered for a proper description of the various past that this phase is not truly cubic but composed of disordered forms of “ice Ic” encountered. cubic and hexagonal stacking sequences. The complexity of the König identified what he called cubic ice 70 y ago (11) by stacking disorder, however, appears to have been largely over- condensing water vapor to a cold support in the electron mi- looked in most of the literature.
    [Show full text]
  • A Primer on Ice
    A Primer on Ice L. Ridgway Scott University of Chicago Release 0.3 DO NOT DISTRIBUTE February 22, 2012 Contents 1 Introduction to ice 1 1.1 Lattices in R3 ....................................... 2 1.2 Crystals in R3 ....................................... 3 1.3 Comparingcrystals ............................... ..... 4 1.3.1 Quotientgraph ................................. 4 1.3.2 Radialdistributionfunction . ....... 5 1.3.3 Localgraphstructure. .... 6 2 Ice I structures 9 2.1 IceIh........................................... 9 2.2 IceIc........................................... 12 2.3 SecondviewoftheIccrystalstructure . .......... 14 2.4 AlternatingIh/Iclayeredstructures . ........... 16 3 Ice II structure 17 Draft: February 22, 2012, do not distribute i CONTENTS CONTENTS Draft: February 22, 2012, do not distribute ii Chapter 1 Introduction to ice Water forms many different crystal structures in its solid form. These provide insight into the potential structures of ice even in its liquid phase, and they can be used to calibrate pair potentials used for simulation of water [9, 14, 15]. In crowded biological environments, water may behave more like ice that bulk water. The different ice structures have different dielectric properties [16]. There are many crystal structures of ice that are topologically tetrahedral [1], that is, each water molecule makes four hydrogen bonds with other water molecules, even though the basic structure of water is trigonal [3]. Two of these crystal structures (Ih and Ic) are based on the same exact local tetrahedral structure, as shown in Figure 1.1. Thus a subtle understanding of structure is required to differentiate them. We refer to the tetrahedral structure depicted in Figure 1.1 as an exact tetrahedral structure. In this case, one water molecule is in the center of a square cube (of side length two), and it is hydrogen bonded to four water molecules at four corners of the cube.
    [Show full text]
  • Arxiv:2004.08465V2 [Cond-Mat.Stat-Mech] 11 May 2020
    Phase equilibrium of liquid water and hexagonal ice from enhanced sampling molecular dynamics simulations Pablo M. Piaggi1 and Roberto Car2 1)Department of Chemistry, Princeton University, Princeton, NJ 08544, USA a) 2)Department of Chemistry and Department of Physics, Princeton University, Princeton, NJ 08544, USA (Dated: 13 May 2020) We study the phase equilibrium between liquid water and ice Ih modeled by the TIP4P/Ice interatomic potential using enhanced sampling molecular dynamics simulations. Our approach is based on the calculation of ice Ih-liquid free energy differences from simulations that visit reversibly both phases. The reversible interconversion is achieved by introducing a static bias potential as a function of an order parameter. The order parameter was tailored to crystallize the hexagonal diamond structure of oxygen in ice Ih. We analyze the effect of the system size on the ice Ih-liquid free energy differences and we obtain a melting temperature of 270 K in the thermodynamic limit. This result is in agreement with estimates from thermodynamic integration (272 K) and coexistence simulations (270 K). Since the order parameter does not include information about the coordinates of the protons, the spontaneously formed solid configurations contain proton disorder as expected for ice Ih. I. INTRODUCTION ture forms in an orientation compatible with the simulation box9. The study of phase equilibria using computer simulations is of central importance to understand the behavior of a given model. However, finding the thermodynamic condition at II. CRYSTAL STRUCTURE OF ICE Ih which two or more phases coexist is particularly hard in the presence of first order phase transitions.
    [Show full text]
  • Calving Processes and the Dynamics of Calving Glaciers ⁎ Douglas I
    Earth-Science Reviews 82 (2007) 143–179 www.elsevier.com/locate/earscirev Calving processes and the dynamics of calving glaciers ⁎ Douglas I. Benn a,b, , Charles R. Warren a, Ruth H. Mottram a a School of Geography and Geosciences, University of St Andrews, KY16 9AL, UK b The University Centre in Svalbard, PO Box 156, N-9171 Longyearbyen, Norway Received 26 October 2006; accepted 13 February 2007 Available online 27 February 2007 Abstract Calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world. Calving rates can increase dramatically in response to increases in velocity and/or retreat of the glacier margin, with important implications for sea level change. Despite their importance, calving and related dynamic processes are poorly represented in the current generation of ice sheet models. This is largely because understanding the ‘calving problem’ involves several other long-standing problems in glaciology, combined with the difficulties and dangers of field data collection. In this paper, we systematically review different aspects of the calving problem, and outline a new framework for representing calving processes in ice sheet models. We define a hierarchy of calving processes, to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events. The first-order control on calving is the strain rate arising from spatial variations in velocity (particularly sliding speed), which determines the location and depth of surface crevasses. Superimposed on this first-order process are second-order processes that can further erode the ice margin.
    [Show full text]
  • Jökulhlaups in Skaftá: a Study of a Jökul- Hlaup from the Western Skaftá Cauldron in the Vatnajökull Ice Cap, Iceland
    Jökulhlaups in Skaftá: A study of a jökul- hlaup from the Western Skaftá cauldron in the Vatnajökull ice cap, Iceland Bergur Einarsson, Veðurstofu Íslands Skýrsla VÍ 2009-006 Jökulhlaups in Skaftá: A study of jökul- hlaup from the Western Skaftá cauldron in the Vatnajökull ice cap, Iceland Bergur Einarsson Skýrsla Veðurstofa Íslands +354 522 60 00 VÍ 2009-006 Bústaðavegur 9 +354 522 60 06 ISSN 1670-8261 150 Reykjavík [email protected] Abstract Fast-rising jökulhlaups from the geothermal subglacial lakes below the Skaftá caul- drons in Vatnajökull emerge in the Skaftá river approximately every year with 45 jökulhlaups recorded since 1955. The accumulated volume of flood water was used to estimate the average rate of water accumulation in the subglacial lakes during the last decade as 6 Gl (6·106 m3) per month for the lake below the western cauldron and 9 Gl per month for the eastern caul- dron. Data on water accumulation and lake water composition in the western cauldron were used to estimate the power of the underlying geothermal area as ∼550 MW. For a jökulhlaup from the Western Skaftá cauldron in September 2006, the low- ering of the ice cover overlying the subglacial lake, the discharge in Skaftá and the temperature of the flood water close to the glacier margin were measured. The dis- charge from the subglacial lake during the jökulhlaup was calculated using a hypso- metric curve for the subglacial lake, estimated from the form of the surface cauldron after jökulhlaups. The maximum outflow from the lake during the jökulhlaup is esti- mated as 123 m3 s−1 while the maximum discharge of jökulhlaup water at the glacier terminus is estimated as 97 m3 s−1.
    [Show full text]
  • Ice Flow Impacts the Firn Structure of Greenland's Percolation Zone
    University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 2019 Ice Flow Impacts the Firn Structure of Greenland's Percolation Zone Rosemary C. Leone University of Montana, Missoula Follow this and additional works at: https://scholarworks.umt.edu/etd Part of the Glaciology Commons Let us know how access to this document benefits ou.y Recommended Citation Leone, Rosemary C., "Ice Flow Impacts the Firn Structure of Greenland's Percolation Zone" (2019). Graduate Student Theses, Dissertations, & Professional Papers. 11474. https://scholarworks.umt.edu/etd/11474 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. ICE FLOW IMPACTS THE FIRN STRUCTURE OF GREENLAND’S PERCOLATION ZONE By ROSEMARY CLAIRE LEONE Bachelor of Science, Colorado School of Mines, Golden, CO, 2015 Thesis presented in partial fulfillMent of the requireMents for the degree of Master of Science in Geosciences The University of Montana Missoula, MT DeceMber 2019 Approved by: Scott Whittenburg, Dean of The Graduate School Graduate School Dr. Joel T. Harper, Chair DepartMent of Geosciences Dr. Toby W. Meierbachtol DepartMent of Geosciences Dr. Jesse V. Johnson DepartMent of Computer Science i Leone, RoseMary, M.S, Fall 2019 Geosciences Ice Flow Impacts the Firn Structure of Greenland’s Percolation Zone Chairperson: Dr. Joel T. Harper One diMensional siMulations of firn evolution neglect horizontal transport as the firn column Moves down slope during burial.
    [Show full text]
  • Genesis and Geographical Aspects of Glaciers - Vladimir M
    HYDROLOGICAL CYCLE – Vol. IV - Genesis and Geographical Aspects of Glaciers - Vladimir M. Kotlyakov GENESIS AND GEOGRAPHICAL ASPECTS OF GLACIERS Vladimir M. Kotlyakov Institute of Geography, Russian Academy of Sciences, Moscow, Russia Keywords: Chionosphere, cryosphere, equilibrium line, firn line, glacial climate, glacier, glacierization, glaciosphere, ice, seasonal snow line, snow line, snow-patch Contents 1. Introduction 2. Properties of natural ice 3. Cryosphere, glaciosphere, chionosphere 4. Snow-patches and glaciers 5. Basic boundary levels of snow and ice 6. Measures of glacierization 7. Occurrence of glaciers 8. Present-day glacierization of the Arctic Glossary Bibliography Biographical Sketch Summary There exist ten crystal variants of ice and one amorphous form in Nature, however only one form ice-1 is distributed on the Earth. Ten other ice variants steadily exist only under a certain combinations of pressure, specific volume and temperature of medium, and those are not typical for our planet. The ice density is less than that of water by 9%, and owing to this water reservoirs are never totally frozen., Thus life is sustained in them during the winter time. As a rule, ice is much cleaner than water, and specific gas-ice compounds called as crystalline hydrates are found in ice. Among the different spheres surrounding our globe there are cryosphere (sphere of the cold), glaciosphere (sphere of snow and ice) and chionosphere (that part of the troposphere where the annual amount of solid precipitation exceeds their losses). The chionosphere envelopes the Earth with a shell 3 to 5 km in thickness. In the present epoch, snow and ice cover 14.2% of the planet’s surface and more than half of the land surface.
    [Show full text]
  • Comparison of Remote Sensing Extraction Methods for Glacier Firn Line- Considering Urumqi Glacier No.1 As the Experimental Area
    E3S Web of Conferences 218, 04024 (2020) https://doi.org/10.1051/e3sconf/202021804024 ISEESE 2020 Comparison of remote sensing extraction methods for glacier firn line- considering Urumqi Glacier No.1 as the experimental area YANJUN ZHAO1, JUN ZHAO1, XIAOYING YUE2and YANQIANG WANG1 1College of Geography and Environmental Science, Northwest Normal University, Lanzhou, China 2State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources/Tien Shan Glaciological Station, Chinese Academy of Sciences, Lanzhou, China Abstract. In mid-latitude glaciers, the altitude of the snowline at the end of the ablating season can be used to indicate the equilibrium line, which can be used as an approximation for it. In this paper, Urumqi Glacier No.1 was selected as the experimental area while Landsat TM/ETM+/OLI images were used to analyze and compare the accuracy as well as applicability of the visual interpretation, Normalized Difference Snow Index, single-band threshold and albedo remote sensing inversion methods for the extraction of the firn lines. The results show that the visual interpretation and the albedo remote sensing inversion methods have strong adaptability, alonger with the high accuracy of the extracted firn line while it is followed by the Normalized Difference Snow Index and the single-band threshold methods. In the year with extremely negative mass balance, the altitude deviation of the firn line extracted by different methods is increased. Except for the years with extremely negative mass balance, the altitude of the firn line at the end of the ablating season has a good indication for the altitude of the balance line.
    [Show full text]
  • Glacier (And Ice Sheet) Mass Balance
    Glacier (and ice sheet) Mass Balance The long-term average position of the highest (late summer) firn line ! is termed the Equilibrium Line Altitude (ELA) Firn is old snow How an ice sheet works (roughly): Accumulation zone ablation zone ice land ocean • Net accumulation creates surface slope Why is the NH insolation important for global ice• sheetSurface advance slope causes (Milankovitch ice to flow towards theory)? edges • Accumulation (and mass flow) is balanced by ablation and/or calving Why focus on summertime? Ice sheets are very sensitive to Normal summertime temperatures! • Ice sheet has parabolic shape. • line represents melt zone • small warming increases melt zone (horizontal area) a lot because of shape! Slightly warmer Influence of shape Warmer climate freezing line Normal freezing line ground Furthermore temperature has a powerful influence on melting rate Temperature and Ice Mass Balance Summer Temperature main factor determining ice growth e.g., a warming will Expand ablation area, lengthen melt season, increase the melt rate, and increase proportion of precip falling as rain It may also bring more precip to the region Since ablation rate increases rapidly with increasing temperature – Summer melting controls ice sheet fate* – Orbital timescales - Summer insolation must control ice sheet growth *Not true for Antarctica in near term though, where it ʼs too cold to melt much at surface Temperature and Ice Mass Balance Rule of thumb is that 1C warming causes an additional 1m of melt (see slope of ablation curve at right)
    [Show full text]
  • Glaciers and Their Significance for the Earth Nature - Vladimir M
    HYDROLOGICAL CYCLE – Vol. IV - Glaciers and Their Significance for the Earth Nature - Vladimir M. Kotlyakov GLACIERS AND THEIR SIGNIFICANCE FOR THE EARTH NATURE Vladimir M. Kotlyakov Institute of Geography, Russian Academy of Sciences, Moscow, Russia Keywords: Chionosphere, cryosphere, glacial epochs, glacier, glacier-derived runoff, glacier oscillations, glacio-climatic indices, glaciology, glaciosphere, ice, ice formation zones, snow line, theory of glaciation Contents 1. Introduction 2. Development of glaciology 3. Ice as a natural substance 4. Snow and ice in the Nature system of the Earth 5. Snow line and glaciers 6. Regime of surface processes 7. Regime of internal processes 8. Runoff from glaciers 9. Potentialities for the glacier resource use 10. Interaction between glaciation and climate 11. Glacier oscillations 12. Past glaciation of the Earth Glossary Bibliography Biographical Sketch Summary Past, present and future of glaciation are a major focus of interest for glaciology, i.e. the science of the natural systems, whose properties and dynamics are determined by glacial ice. Glaciology is the science at the interfaces between geography, hydrology, geology, and geophysics. Not only glaciers and ice sheets are its subjects, but also are atmospheric ice, snow cover, ice of water basins and streams, underground ice and aufeises (naleds). Ice is a mono-mineral rock. Ten crystal ice variants and one amorphous variety of the ice are known.UNESCO Only the ice-1 variant has been – reve EOLSSaled in the Nature. A cryosphere is formed in the region of interaction between the atmosphere, hydrosphere and lithosphere, and it is characterized bySAMPLE negative or zero temperature. CHAPTERS Glaciology itself studies the glaciosphere that is a totality of snow-ice formations on the Earth's surface.
    [Show full text]
  • Theoretical Design of a Non-Cyclic Cooling System Using Pykrete As a Cooling Material and Considering the System As a Heat Exchanger
    International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2013): 6.14 | Impact Factor (2015): 6.391 Theoretical Design of a Non-Cyclic Cooling System using Pykrete as a Cooling Material and Considering the System as a Heat Exchanger Divyashree Deore1, Sarthak Sharma2 B.E. Mechanical Engineering, Sinhgad Academy of Engineering, Pune, Maharashtra, India Abstract: A non-cyclic cooling unit was theoretically designed with supply of air similar to that of commercially available A.C. unit producing one ton of refrigeration. The minimum temperature for the design was considered to be 16℃. The element used for cooling the air is Pykrete. The various stable temperatures of Pykrete were experimentally found. Also, the cooling capacity of designed unit was found theoretically. The working principle of this system is similar to that of Thermal Energy Storage system. The calculations were carried out considering this system would act as a heat exchanger. Keywords: Non-Cyclic Cooling System, Pykrete, Stable Surface temperatures, Thermal Energy Storage System, Heat Exchanger 1. Introduction many months later, at individual building, multiuser building, district, town or even regional scale depending on In this method Pykrete is used for keeping the space at the specific technology. As examples: energy demand can be temperature below the surrounding temperature. Pykrete is a balanced between day time and night time; summer heat frozen composite material made of approximately 14 percent from solar collectors can be stored inter-seasonally for use in sawdust or some other form of wood pulp (such as paper) winter; and cold obtained from winter air can be provided and 86 percent ice by weight (6 to 1 by weight).
    [Show full text]