2. Glacier ice: definitions and dynamics

The shape and size of glacier ice bodies (their morphology) is dictated by the interplay between climate and topography, and a classification scheme has been adopted to cover all the variants that lie on a spatial and temporal continuum of morphologies. ‘Glacier ice: definitions and dynamics’ explains that in any one location over time different glacier morphologies may evolve. It describes how water as a liquid is fundamental to glacial processes, and considers a range of glacier dynamics and flow mechanics, including the processes and causes of ice deformation, creeping ice, sliding beds, and glacial surge. It also explains subglacial bed deformation, a relatively newly discovered process that emerged only in the 1970s.

Subaqueous calving margin morphology at Mueller, Hooker and Tasman glaciers in Aoraki/Mount Cook National Park, New Zealand

Journal of Glaciology ◽

10.3189/2012jog12j048 ◽

2012 ◽

Vol 58 (212) ◽

pp. 1037-1046 ◽

Cited By ~ 19

Author(s):

Clare M. Robertson ◽

Douglas I. Benn ◽

Martin S. Brook ◽

lan C. Fuller ◽

Kat A. Holt

Keyword(s):

National Park ◽

Lake Level ◽

Thick Layer ◽

Unique Combination ◽

Bathymetric Data ◽

Proglacial Lakes ◽

Glacier Dynamics ◽

Debris Cover ◽

Glacier Ice ◽

AbstractThe subaqueous margins of calving glaciers have the potential to make significant contributions to glacier mass loss. However, to date, very little is known about the morphology and development of subaqueous margins. A unique combination of sub-bottom profile and bathymetric data collected between 2008 and 2010 in proglacial lakes at Mueller, Hooker and Tasman glaciers in New Zealand’s Southern Alps reveal subaqueous ice ramps extending up to 510 m from the terminus of each glacier. Ice ramp surfaces are undulating and covered with a thick layer (up to 10 m) of unsorted sediment derived from supraglacial and englacial debris, lateral moraines and deltaic deposits. A cyclic calving pattern, relatively stable lake level and the debris cover appear to control the development and maintenance of these ice ramps. High subaerial retreat rates generally correspond to high subaqueous calving rates, although the highest subaerial retreat rates are not associated with the largest ice ramp. Debris mantling the subaqueous ice ramp surfaces insulates the ice from melting and also reduces buoyant forces acting on the terminus. Comparisons with previous studies show that the ice ramps evolve over time with changes in glacier dynamics and water-body properties.

Supraglacial debris-transport variability over time: examples from Switzerland and Iceland

Annals of Glaciology ◽

10.1017/s0260305500015391 ◽

1996 ◽

Vol 22 ◽

pp. 181-186 ◽

Cited By ~ 2

Author(s):

W.B. Whalley ◽

C.F. Palmer ◽

S.J. Hamilton ◽

D. Kitchen

Keyword(s):

19Th Century ◽

Little Ice Age ◽

Ice Age ◽

Debris Transport ◽

Actual Volume ◽

Glacier Ice ◽

Rock Glaciers ◽

Slow Moving ◽

The 19Th Century ◽

The volume of debris in the left-lateral, Little Ice Age (LIA:AD1550–1850) moraine of the Feegletscher, Valais, Switzerland was compared with the actual volume being transported currently by the glacier. The latter is smaller by a factor of about two. In Tröllaskagi, north Iceland, a surface cover of debris on top of a very slow moving glacier ice mass (glacier noir, rock glacier) has been dated by lichenometry. The age of the oldest part is commensurate with LIA moraines in the area. Knowing the volume of debris of a given age allows an estimate of the debris supply to the glacier in a given time. Again, there appears to have been a significant reduction in debris to the glacier since the turn of the 19th century. Debris input in the early LIA seems to have been particularly copious and this may be important in the formation of some glacier depositional forms such as rock glaciers.

Later, laterculus, and testa. New Perspectives on Latin brick terminology

Opuscula Annual of the Swedish Institutes at Athens and Rome ◽

10.30549/opathrom-09-02 ◽

2016 ◽

Vol 9 ◽

pp. 7-31

Author(s):

Henrik Gerding

Keyword(s):

Roof Tile ◽

Imperial Period ◽

Fired Bricks ◽

Standard Term ◽

Mud Bricks ◽

Material Record ◽

Over Time ◽

For centuries antiquarians and archaeologists have tried to reconcile the terminology of ancient writers on architecture, such as Vitruvius, with the perceived realities of the material record. One particular issue of debate concerns the interpretation of different words for “brick” in Latin. In this paper it is argued that earlier attempts to settle this question are unsatisfactory and leave several problems unresolved. A thorough examination of literary and epigraphic sources, combined with new insights in Hellenistic brick usage, suggests that primary distinctions in Latin brick terminology were based on shape and size, rather than on a mere division between fired and unfired bricks. Thus, it is argued that later basically signified a large moulded block, but normally was used to indicate mud bricks; that laterculus changed over time from being a diminutive (a small later) to becoming the standard term for the relatively thin fired bricks of the Roman Imperial period; and that testa originally and primarily signified a fragment of a roof tile (or a potsherd), but from the 1st century AD also may designate typical Roman Imperial bricks, after they have been divided into smaller, often triangular, pieces.

Annual River Runoff Variations and Trends for the Andes Cordillera

Journal of Hydrometeorology ◽

10.1175/jhm-d-17-0094.1 ◽

2018 ◽

Vol 19 (7) ◽

pp. 1167-1189 ◽

Cited By ~ 3

Author(s):

Sebastian H. Mernild ◽

Glen E. Liston ◽

Christopher A. Hiemstra ◽

Jacob C. Yde ◽

Gino Casassa

Keyword(s):

River Runoff ◽

Annual Runoff ◽

Spatiotemporal Variability ◽

Modeling Tools ◽

Ice Melt ◽

The Andes ◽

Glacier Ice ◽

High Runoff ◽

Over Time ◽

Andes Cordillera

Abstract We analyzed modeled river runoff variations west of the Andes Cordillera’s continental divide for 1979/80–2013/14 (35 years). Our foci were annual runoff conditions, runoff origins (rain, snowmelt, and glacier ice), and runoff spatiotemporal variability. Low and high runoff conditions were defined as occurrences that fall outside the 10th (low values) and 90th (high values) percentile values of the period of record. SnowModel and HydroFlow modeling tools were used at 4-km horizontal grid increments and 3-h time intervals. NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) datasets were used as atmospheric forcing. This modeling system includes evaporation and sublimation from snow-covered surfaces, but it does not take into account evapotranspiration from bare and vegetation-covered soils and from river and lake surfaces. In general for the Andes Cordillera, the simulated runoff decreased before 1997 and increased afterward. This could be due to a model precipitation artifact in the MERRA forcing. If so, this artifact would influence the number of years with low runoff values, which decreased over time, while the number of high runoff values increased over time. For latitudes south of ~40°S, both the greatest decrease in the number of low runoff values and the greatest increase in high runoff values occurred. High runoff values averaged 84% and 58% higher than low values for nonglacierized and glacierized catchments, respectively. Furthermore, for glacierized catchments, 61% and 62% of the runoff originated from rain-derived runoff during low and high runoff extreme years, respectively; 28% and 30% from snowmelt-derived runoff; and 11% and 8% from glacier-ice-melt-derived runoff. As the results could be MERRA dependent, more work with other precipitation forcings and/or in situ measurements is needed to assess whether these are real runoff behaviors or artifacts.

Longitudinal Stability of LD Subtypes Based on Age- and IQ-Achievement Discrepancies

Learning Disability Quarterly ◽

10.2307/1510467 ◽

1986 ◽

Vol 9 (3) ◽

pp. 214-225 ◽

Cited By ~ 13

Author(s):

Elizabeth J. Short ◽

Lynne Feagans ◽

James D. McKinney ◽

Mark I. Appelbaum

Keyword(s):

Reading Achievement ◽

Classification System ◽

Classification Scheme ◽

Learning Disabled ◽

Longitudinal Stability ◽

Slow Learners ◽

Educational Implications ◽

A twofold classification system based on discrepancy formulas was employed to subtype normal (NLD) and learning disabled (LD) children into educationally meaningful groups based upon simultaneous consideration of IQ-achievement and age-achievement discrepancies. 52 LD and 58 NLD children were classified into five groups: overachievers, target achievers, underachievers, slow learners, and disabled achievers. This classification system appeared useful by its ability to differentiate disabled learners, who were discrepant in reading achievement as predicted by both age and IQ, from slow learners, who were only discrepant in reading achievement as predicted by age. The longitudinal stability of the classification scheme was examined over a 3-year period. As expected, NLD students' achievement was more predictable over time than their LD peers' LD students became more disabled with age in spite of remedial services. The educational implications and theoretical relevance of discrepancy-based subtypes are discussed.

Collocative Integrity and Our Many Varied Subjects: What the Metric of Alignment between Classification Scheme and Indexer Tells Us About Langridge’s Theory of Indexing

NASKO ◽

10.7152/nasko.v4i1.14660 ◽

2013 ◽

Vol 4 (1) ◽

pp. 196 ◽

Cited By ~ 1

Author(s):

Joseph T. Tennis

Keyword(s):

Language Change ◽

Classification Scheme ◽

Conceptual Models ◽

Complex Relationship ◽

Change Over Time ◽

Classification Schemes ◽

The One ◽

The Universe ◽

<p>As the universe of knowledge and subjects change over time, indexing languages like classification schemes, accommodate that change by restructuring. Restructuring indexing languages affects indexer and cataloguer work. Subjects may split or lump together. They may disappear only to reappear later. And new subjects may emerge that were assumed to be already present, but not clearly articulated (Miksa, 1998). In this context we have the complex relationship between the indexing language, the text being described, and the already described collection (Tennis, 2007). It is possible to imagine indexers placing a document into an outdated class, because it is the one they have already used for their collection. However, doing this erases the semantics in the present indexing language. Given this range of choice in the context of indexing language change, the question arises, what does this look like in practice? How often does this occur? Further, what does this phenomenon tell us about subjects in indexing languages? Does the practice we observe in the reaction to indexing language change provide us evidence of conceptual models of subjects and subject creation? If it is incomplete, but gets us close, what evidence do we still require?</p>

Supraglacial debris-transport variability over time: examples from Switzerland and Iceland

Annals of Glaciology ◽

10.3189/1996aog22-1-181-186 ◽

1996 ◽

Vol 22 ◽

pp. 181-186 ◽

Cited By ~ 2

Author(s):

W.B. Whalley ◽

C.F. Palmer ◽

S.J. Hamilton ◽

D. Kitchen

Keyword(s):

19Th Century ◽

Little Ice Age ◽

Ice Age ◽

Debris Transport ◽

Actual Volume ◽

Glacier Ice ◽

Rock Glaciers ◽

Slow Moving ◽

The 19Th Century ◽

The volume of debris in the left-lateral, Little Ice Age (LIA: AD 1550–1850) moraine of the Feegletscher, Valais, Switzerland was compared with the actual volume being transported currently by the glacier. The latter is smaller by a factor of about two. In Tröllaskagi, north Iceland, a surface cover of debris on top of a very slow moving glacier ice mass (glacier noir, rock glacier) has been dated by lichenometry. The age of the oldest part is commensurate with LIA moraines in the area. Knowing the volume of debris of a given age allows an estimate of the debris supply to the glacier in a given time. Again, there appears to have been a significant reduction in debris to the glacier since the turn of the 19th century. Debris input in the early LIA seems to have been particularly copious and this may be important in the formation of some glacier depositional forms such as rock glaciers.

Synthesis and Characterization of Gold Nanoparticles by Aluminum as a Reducing Agent

Baghdad Science Journal ◽

10.21123/bsj.2020.17.1(suppl.).336 ◽

2020 ◽

Vol 17 (1(Suppl.)) ◽

pp. 336

Author(s):

Mazin K. Hamid et al.

Keyword(s):

Reduction Process ◽

Synthesis And Characterization ◽

Arabic Gum ◽

Synthesis Of Nanoparticles ◽

Color Changes ◽

Aluminum Metal ◽

Size Of Particles ◽

Over Time ◽

The synthesis of nanoparticles (GNPs) from the reduction of HAuCl4 .3H2O by aluminum metal was obtained in aqueous solution with the use of Arabic gum as a stabilizing agent. The GNPs were characterized by TEM, AFM and Zeta potential spectroscopy. The reduction process was monitored over time by measuring ultraviolet spectra at a range of λ 520-525 nm. Also the color changes from yellow to ruby red, shape and size of GNP was studied by TEM. Shape was spherical and the size of particles was (12-17.5) nm. The best results were obtained at pH 6.

The effect of conventional preservatives on spicule length of Heligmosomoides bakeri (Nematoda, Heligmosomidae)

Journal of Helminthology ◽

10.1017/s0022149x21000596 ◽

2021 ◽

Vol 95 ◽

Author(s):

M. Musah-Eroje ◽

L. Burton ◽

J.M. Behnke

Keyword(s):

Salt Solution ◽

Room Temperature ◽

Taxonomic Character ◽

Time Intervals ◽

Closely Related Species ◽

Spicule Length ◽

Heligmosomoides Bakeri ◽

Key Characters ◽

Over Time ◽

Abstract Nematode spicules vary in shape and size even between closely related species and, therefore, constitute key characters in nematode taxonomy for distinguishing between species. Spicules are seldom measured on fresh specimens, but rather at some time after extraction from culled hosts and after a period of preservation of the worms in chemical fixatives or by freezing. We carried out two experiments to assess the effects of freezing in Hanks’ balanced salt solution, 70% or 80% ethanol and 10% formalin (both of the latter at room temperature and after storage at −80°C) on spicule length of Heligmosomoides bakeri at two time intervals after extraction from mice (Experiment 1, one and four weeks; Experiment 2, one and four months). In Experiment 1, no significant differences were detected, although there was some variation between treatments and over time. In Experiment 2, spicule length varied significantly between treatments and over time, the greatest shrinkage being in 80% ethanol and the least in 10% formalin. However, overall variation in spicule length was very limited, accounting for no more than 5.03% change in length over time and 4.95% between treatments at any of the periods of assessment. Therefore, while whole nematodes can shrivel and shrink in preservatives, making many measurements unreliable, our data indicated that spicule lengths are very little changed by preservation techniques over time, and so spicule length remains as a reliable taxonomic character.

Reassessing the flow law of glacier ice using satellite observations

10.31223/x5d32x ◽

2021 ◽

Author(s):

Joanna Millstein ◽

Brent Minchew ◽

Samuel Pegler

Keyword(s):

Viscous Flow ◽

Satellite Observations ◽

Ice Flow ◽

Ice Shelves ◽

Accurate Representation ◽

Flow Models ◽

Glacier Dynamics ◽

Glacier Ice ◽

Flow Law ◽

Range Of Values

Accurate representation of the viscous flow of ice is fundamental to understanding glacier dynamics and projecting sea-level rise. Ice viscosity is often described by a simple but largely untested and uncalibrated constitutive relation, Glen’s Flow Law, wherein the rate of deformation is proportional to stress raised to the power n. The value n = 3 is commonly prescribed in ice-flow models, though observations and experiments support a range of values across stresses and temperatures found on Earth. Here, we leverage recent remotely-sensed observations of Antarctic ice shelves to show that Glen’s Flow Law approximates the viscous flow of ice with n = 4.1 ± 0.4 in fast-flowing areas. The viscosity and flow rate of ice are therefore more sensitive to changes in stress than most ice-flow models allow.