bluuebunny/crossref_metadata_2025 huggingface dataset:
VALUASI PENGENDALIAN EMISI BOILER BATU BARA PADA INDUSTRI KERTAS DAN ESTIMASI EMISI MERKURI (Hg) (VALUATION ON EMISSION CONTROL OF COAL-FIRED BOILER OF PAPER INDUSTRY AND ESTIMATION OF MERCURY (Hg) EMISSION)
Authors: Setiawan Yusup
Published: September 2017

Steam and electricity needs in the paper industry have been provided itself through coal-fired boiler equipped with emission control devices. Boiler flue gas emissions of coal combustion products contain contaminants such as particulate emissions , NO2 and SO2 , and a small amount of emissions of mercury (Hg). Valuation on boiler emissions quality associated with air emissions control systems and emissions standard has been carried out. Estimation of mercury concentration in air emissions of boiler flue gas in the paper industry has also been conducted. The valuation on the air emissions quality of non-mercury parameters of paper industry boilers has also been done based on national emissions standards. The results of the valuation indicated that the current applied of flue gas emissions control devices in the paper industry has been optimally operated so that the emission quality of boiler for both non-mercury parameters and mercury parameters has been complied with the emission quality standards. Prediction of mercury content in air emissions of a coal boiler stack of paper industry that is discharged into environment based on the content of mercury in coal is 0.0205 mg/Nm3 (20.5 µg/Nm3 ) maximum. Paper industry needs to consider the application of co-benefit technology when mercury is used as a quality standard emissions parameter. ABSTRAKKebutuhan uap dan atau listrik pada industri kertas disediakan melalui unit boiler berbahan bakar batu bara yang dilengkapi alat pengendali emisi. Emisi gas boiler mengandung pencemar berupa partikulat, NO2 dan SO2 , dan merkuri (Hg). Valuasi kualitas emisi boiler berkaitan dengan sistem pengendalian emisi udara dan baku mutu emisi telah dilakukan, Estimasi kadar merkuri di udara emisi cerobong boiler pada industri kertas juga telah dilakukan. Valuasi kualitas emisi udara non-merkuri emisi boiler industri kertas juga telah dilakukan berdasarkan baku mutu emisi nasional. Hasil valuasi menunjukkan bahwa alat pengendali emisi gas buang boiler yang telah diterapkan saat ini pada industri kertas telah dioperasikan secara optimal sehingga kualitas emisi boiler baik untuk parameter non-merkuri maupun untuk parameter merkuri telah memenuhi baku mutu emisi. Prediksi kadar merkuri dalam udara emisi cerobong boiler batu bara industri kertas yang dibuang ke lingkungan dihitung berdasarkan kadar merkuri dalam batu bara adalah maksimum sebesar 0,0205 mg/Nm3 (20,5 µg/Nm3 ). Industri kertas perlu mempertimbangkan penerapan teknologi co-benefit bilamana suatu saat parameter merkuri ditetapkan sebagai parameter baku mutu emisi.
A Century of Library Support for Teacher Education in Calgary
Authors: Brydges Barbara
Published: September 2017

This paper traces the century-long history of a library that has served teacher preparation programs in Calgary, Alberta, since 1909. It looks at how this library’s role and collections adapted to shifting notions of what constituted good teacher education and changing economic circumstances. In recounting this history, the paper examines the historical circumstances that created a separate education library at the University of Calgary and how issues of group and professional identity contributed to its continuing existence. The various themes which emerge may be common to many North American education libraries.
The Test Collection at ETS: 34 Years and Still Growing;
Authors: McQuillen Karen
Published: September 2017

This essay updates the following two articles that were previously published in the Winter 1975/1976 and 1984 issues respectively of Education Libraries, and featured the ETS Test Collection.
Resources on the Net: Past, Present, and Future of Academic Libraries
Authors: Bober Chris
Published: September 2017

[...]
Filling in the Blanks
Authors: Snider Jacqueline
Published: September 2017

One of the perks of living in a university town is that distinguished academics often visit. I heard Dr. Peter Stallybras of the University of Pennsylvania talk about “blanks” and the importance of writing. [...]
New and Forthcoming
Authors: Mestre Lori
Published: September 2017

[...]
Book Reviews
Authors: Smith Mikki , Keiser Barbie E. , Wadham Rachel L. , Kirven Sheila , Jacobs Warren
Published: September 2017

[...]
A Collaborative approach to implementing 21st Century skills in a High school senior research class
Authors: O'Sullivan Michael K. , Dallas Kim B.
Published: September 2017

Businesses and higher education leaders are looking for students with the ability to evaluate and analyze information and to use this information to solve real-world problems. These are the information literacy skills students need for the 21st century. However, several recent studies on the ability of college freshmen to handle the rigor of college courses and research indicate that high school students are not being adequately prepared to apply these skills. The authors provide a case study of a collaborative effort between an English teacher and the high school librarian to better prepare high school seniors on how to locate reliable information, analyze the information and then determine how it can be applied to solving a real world issue or problem.
Using a Student-Generated Survey to Inform Planning For a User-focused Learning Commons
Authors: Weiner Sharon A. , Weiner John M.
Published: September 2017

A master’s comprehensive University is planning a learning commons to support undergraduate learning. The planning process included a literature review, site visits to commons, consultations with experts in the field, discussions with campus specialists, and surveys of patrons. The literature reports two primary forms of data gathering for learning commons: interview/observation and purposive surveys. This report describes the findings of a survey conducted to determine students’ perceptions of services relevant in learning commons. The findings indicated that the students wanted help with their information processing needs.
Shhh! No talking about retention in the library!
Authors: Blackburn Heidi
Published: September 2017

Student retention rates have long been a topic among school administrators, but it is an issue barely mentioned in library circles. This article will discuss the role the academic library can play in increasing and maintaining student retention rates on campus. By focusing briefly on four main topics, including reaching out to students early and often, getting them in the library door and getting them to stay, the reader will be able to see the broad picture of how crucial libraries are to fighting student attrition.
Conserving for the Future by Archiving our Past; A Story about Technology and Digitization Informed by a Vintage Paperback Book Collection
Authors: Werts Cybèle
Published: September 2017

The books, photographs, letters and other ephemera of our past are for the first time becoming completely transformed into the digital bits and bytes of our computer-generated present. What happens to these products as they shift from the corporeal to the technological world? What essence might be lost when a book is scanned into a computer or is part of the Google Book Library Project, and what might be gained? Or is it all energy simply transferred to another medium like when wood is burned in a fireplace turns into to heat energy? This extended article explores these questions using a collection of vintage magazines and paperback books, which provide a lighthearted timbre to a somewhat esoteric subject.
Book Reviews
Authors: Keiser Barbie , Jacobs Warren , Niedbala Mona Anne , Moore Celeste
Published: September 2017

[...]
Guest Editorial
Authors: Ramachandran Hema , Lanham Erin
Published: September 2017

This issue of Education Libraries, which is dedicated to the ongoing, timely, and important topic of information literacy in the workplace, showcases presentations from two sessions sponsored by the Education and Engineering Divisions at the 2010 SLA Annual Conference in New orleans http://www.sla.org/content/events/confpresentations/2010.cfm. The first part of the program provided an overview of the issues from key researchers in the field; the second part was a panel of academic and corporate engineering librarians discussing the challenges they face in imparting information literacy. [...]
21st Century Workforce Initiatives: Implications for Information Literacy Instruction in Academic Libraries
Authors: Leavitt Laura L.
Published: September 2017

The discussion that follows is designed to expose the reader to a selection of educational reform initiatives that fall under the “21st Century Workforce” umbrella. The aims of these initiatives are quite harmonious with the overarching goals of librarianship and the opportunities for librarians to become involved and to demonstrate leadership in this arena are plentiful. The author’s efforts to incorporate information literacy principles and to encourage critical thinking in a graduate level organizational behavior class – in light of these initiatives and in response to employer feedback – are also discussed. It is hoped that the followinginformation will inspire librarians to explore the initiatives further and to re-examine current information literacy and instruction efforts within this larger framework.
The Role of Mentoring in the Leadership Development of Pre-Service School Librarians
Authors: Smith Daniella L.
Published: September 2017

The purpose of this study was to determine how providing pre-service school librarians with mentors during their degree program impacted their level of self-perceived transformational leadership potential. The study consisted of 30 participants enrolled in a school library certification master’s degree program emphasizing leadership. The findings indicated that the use of mentors had a positive impact on the leadership development of the participants. Moreover, the combination of the leadership training and the experience of having a mentor taught the participants the behaviors that are desirable in mentors and encouraged them to apply mentorship as a leadership role in their schools.
Book Reviews
Authors: Keiser Barbie E. , Carhee Dorcas , Guengerich Anna Marie , Wallace Elise D.
Published: September 2017

[...]
Laying the Groundwork For the 90’s; The Education Division of SLA in the 80’s
Authors: Galler Anne M.
Published: September 2017

When Charles Missar, our current Chair of the Division asked me to speak about the Education Division in the 80’s, as the person deeply involved in the Division during that time, it was only after I –foolishly—said yes to giving this address when I realized that although I have been a member of SLA since 1958, long before our Division was formed, I only joined same officially in 1984. This is the bad news. [...]
Resources on the Net: New and Expanding Roles for Libraries
Authors: Bober Chris
Published: September 2017

The Library Publishing Toolkit, a 400 page ebook launched on August 1, 2013, offers libraries interested in expanding into publishing a resource “to identify trends in library publishing, seek out best practices to implement and support such programs, and share the best tools and resources.” A product of the combined efforts of Milne Library at SUNY Geneseo and the Monroe County Library System, the Library Publishing Toolkit “looks at the broad and varied landscape of library publishing through discussions, case studies, and shared resources.” [...]
Book Reviews
Authors: Keiser Barbie E. , Bouwers Samantha
Published: September 2017

[...]
Detecting Earning Management: Deferred Taxes vs Accruals: A Pakistani Perspective
Authors: Shanwari Imran , Shah S. M. Aamir
Published: September 2017

Objective: Earning Management has been one of the major areas of accounting research which has received a great attention in the past and also quite recently. Detecting earning management has always been one of the major areas of concern for the researchers. Earnings Management is pervasive. There are a number of models available to Detect and measure the earnings management activity.

Methodology: The accrual models are the most used models to proxy the discretionary accruals and the earnings management. The effectiveness of the accrual models is somewhat skeptical at times when researchers found some inconsistencies in results while using the accrual models.  The researchers are still finding some better and effective model that can be used to better measure and capture the earnings management activity. The focus of this study is to find out as to whether a deferred tax as compared to accrual models is more useful in measuring or detecting the earnings management in Pakistani perspective. The study is based on the Pakistani companies listed on the Karachi Stock Exchange (KSE). This study is expected to be an addition to the existing research as to whether the models used for detecting earnings management through deferred taxes by Philips et al (2003) are also applicable to Pakistani Scenario which is a developing country. The study used Probit Regression Model with pooled cross sectional data to measure the usefulness of both; accruals and deferred taxes (the proxies)   used as better measure for Earnings management.

Results: The results of the study are inconsistent with the Philips et al. (2003) study. Based on this study it is concluded that deferred tax is not incrementally useful along with the other accrual measure. The accruals models show significant results and are more powerful metric to detect earnings management as compared to the deferred taxes in Pakistan.
Accumulation and hoar effects on microwave emission in the Greenland ice-sheet dry-snow zones
Authors: Abdalati Waleed , Steffen Konrad
Published: September 2017

The relationships between accumulation and microwave emissivity in the dry-snow regions of the Greenland ice sheet are studied with special focus on hoar formation. With the use of a discrete-ordinate radiative-transfer model, the relative contributions of hoar and accumulation to microwave omission are examined. The results show that the link between microwave emission and accumulation rates in the dry-snow area of the Greenland ice sheet is significant; however, the emissivity is also dependent on the extent of hoar development. As a result, accumulation estimates based on passive microwave observations in the low-accumulation dry-snow areas will require successful parameterization of hoar formation. Furthermore, the increasing Tb, trends that were observed during the 1980s, which have been hypothesized to be related to accumulation changes, may be strongly related to variations in hoar development. Other possible explanations for these observed trends, such as slight surface melt or atmospheric conditions, are also discussed.
Glaciohydraulic supercooling: a freeze-on mechanism to create stratified, debris-rich basal ice: I. Field evidence
Authors: Lawson Daniel E. , Strasser Jeffrey C. , Evenson Edward B. , Alley Richard B. , Larson Grahame J. , Arcone Steven A.
Published: September 2017

Debris-laden ice accretes to the base of Matanuska Glacier, Alaska, U.S.A., from water that supercools while flowing in a distributed drainage system tip the adverse slope of an overdeepening. Frazil ice grows in the water column and forms aggregates, while other ice grows on the glacier sole or on substrate materials. Sediment is trapped by this growing ice, forming stratified debris-laden basal ice. Growth rates of >0.l ma−1 of debris-rich basal ice are possible. The large sediment fluxes that this mechanism allows may have implications for interpretation of the widespread deposits from ice that flowed through other overdeepenings, including Heinrich events and the till sheets south of the Laurentian Great Lakes.
Modeling the signature of a transponder in altimeter return data and determination of the reflection surface of the ice cap near the GRIP camp, Greenland
Authors: Haardenog-Pedersen G. , Keller K. , Tscherning C. C. , Gundestrup N.
Published: September 2017

Using an active transponder with the ERS-I and ERS-2 radar altimeters, the distance to the satellite was measured at a location close to the GRIP site, Greenland, at an altitude of 3.2 km. The measurement was executed while the transponder was in the “ice-tracking mode”. It includes a bias due to the propagation delay. The location of the transponder was determined using the global positioning system.

The transponder signal was modeled and the distance from the altimeter to the effective reflection point of the transponder was determined. Since the transponder was located within 1 km of the ground tracks, the measurement was corrected for this offset. A correction was also done for the surface slope, resulting in the distance (plus bias) to the closest sub-satellite point on the surface of the (compact) snow.

The transponder signal was then removed from the radar altimeter waveform, enabling the determination of the distance (plus bias from the altimeter to the first reflective surface within the snow. The différence between this distance and that obtained using the transponder was < 2 m. This shows that the surface which gives rise to the first return of the reflection agrees with the surface of the (compact, dry) snow at this high-altitude location. This is an important result to be used when studying ice-cap topography using satellite radar altimetry.
Glacial retreat and its geomorphologic effects on Mexico’s active volcanoes, 1994–95
Authors: Palacios David , Marcos Javier De
Published: September 2017

The northern slopes of Mexico’s great, active stratovolcanoes, Popocatépetl (5450 m.a.s.l.) and Pico de Orizaba (5700 m a.s.l.), are covered by glaciers. This paper analyzes the retreat of the glaciers between February 1994 and October 1995, and its geo-morphological consequences. The results discussed are a continuation of research conducted on the volcanoes up to 1994. Although the glaciers retreated a great deal during the 1980s and early 1990s, the process accelerated from 1994 to 1995. The heavy erosion that had been observed on the deglaciated walls of the volcanoes during these decades increased as the glaciers retreated. Sediments originating from material loosened from the exposed lateral walls added to the supraglacial layer. Temperature readings taken from boreholes made in the glaciers indicated that ablation had been reduced as a result of the insulating effects of the debris mantle. This allowed widespread formation of deposits that buried ice in areas where the glacier had already disappeared. These results confirmed the conclusions of earlier studies that deglaciation of stratovolcanoes has resulted in the acceleration of slope processes and the formation of buried ice deposits.
Crevasse patterns and the strain-rate tensor: a high-resolution comparison
Authors: Harper J. T. , Humphrey N. F. , Pfeffer W. T.
Published: September 2017

Values of the strain-rate tensor represented at a 20 m length scale are found to explain the pattern and orientation of crevasses in a 0.13 km2 reach of Worthington Glacier, Alaska, U.S.A. The flow field of the reach is constructed from surveyed displacements of 110 markers spaced 20-30 m apart. A velocity gradient method is then used to calculate values of the principal strain-rate axes at the nodes of a 20 m x 20 m orthogonal grid. Crevasses in the study reach are of two types, splaying and transverse, and are everywhere normal to the trajectories of greatest (most tensile) principal strain rate. Splaying crevasses exist where the longitudinal strain rate (x) is ≤ 0 and transverse crevasses are present under longitudinally extending flow (i.e. x > 0). The orientation of crevasses changes in the down-glacier direction, but the calculated rotation by the flow field does not account for this change in orientation. Observations suggest that individual crevasses represent local values of the regional flow field and are transient on the time-scale of 1-2 years; they are not persistent features that are translated and rotated by flow. Crevasse patterns are thus found to be a useful tool for mapping the strain-rate tensor in this reach of a temperate valley glacier.
Altitudinal gradient of mass-balance sensitivity to climatic change from 18 years of observations on glacier d’Argentière, France
Authors: Vallon M. , Vincent C. , Reynaud L.
Published: September 2017

Assessment of the contribution of small glaciers to sea-level rise or the reconstruction of past glacial mass balance requires knowledge of mass-balance sensitivity to climatic variations. The aim of this paper is to clarify this relation. The mass-balance fluctuations analyzed from measurements on glacier d’Argentière, Mont Blanc massif, France, between 1850 and 2700 m a.s.l. were compared with climatic variations at a nearby meteorological station. Statistical study of the data shows that: (1) the annual mass-balance fluctuations are dependent on elevation, and (2) the mass-balance sensitivity to temperature decreases with altitude and diverges from current model results. Consequences of a temperature variation of 1°C for global volume variations are significant. A simple calculation on glacier des Bossons, Mont Blanc massif, France, shows that the sensitivity from the model can lead to volume variations twice as high as results compatible with our observations.
Satellite gravity and the mass balance of the antarctic ice sheet
Authors: Bentley C. R. , Wahr J. M.
Published: September 2017

Changes in the Earth’s gravity field with time have important applications to a broad range of disciplines. Any process that involves a large enough horizontal redistribution of mass, either within the Earth or on or above its surface, is potentially detectable. In particular, when ice sheets grow or shrink, gravity changes as mass is redistributed in the solid earth and between the oceans and the ice sheets. The sources of global sea-level rise (about 2 mm a−1 over the last century) and in particular the contribution of the Antarctic ice sheet thereto are not well understood. Gravity measurements can help to diminish this uncertainty.

The technology currently exists to measure gravity with high accuracy by a dual-satellite mission in which the distance between the satellites is precisely monitored. We estimate from recent studies that temporal changes in the gravity field as determined by a satellite gravity mission lasting 5 years at an orbital height of 400 km would be sensitive to changes in the overall mass of the Antarctic ice sheet to a precision corresponding to better than 0.01 mm a−1 of sea-level change. However, the effects of three other phenomena that could each produce a temporally varying gravity signal with characteristics comparable to that caused by a change in Antarctic ice—postglacial rebound, inter-annual variability in snowfall, and atmospheric pressure trends — also need to be evaluated. Postglacial rebound could be partly separated from ice-mass changes with the aid of global positioning system campaigns and numerical models of rebound that use improved determinations of mantle viscosity also provided by the gravity mission. Determination of inter-annual ice-mass changes will be aided by measurements of moisture-flux divergence around the perimeters of the ice sheets and direct observations of inter-annual changes by the gravity satellite itself. The removal of pressure effects over Antarctica will become more effective as the number of automatic weather stations in the interior of the continent increases.

Even after corrections are made for these factors, the uncertainties they cause limit the accuracy in the détermination of the contribution of the Antarctic ice sheet to sea-level change to about 0.5 mm a−1. However, there is a strong complementarity between gravity measurements and the surface-height measurements that will be produced by NASA’s laser altimeter mission early next century. Together, they should be able to determine that contribution to an accuracy of about 0.1 mm a−1.
A 1 year record of global radiation and albedo in the ablation zone of Morteratschgletscher, Switzerland
Authors: Oerlemans J. , Knap W. H.
Published: September 2017

We analyse data on solar radiation measured with an automatic weather station on Morteratschgletscher, Switzerland, for the period 1 October 1995–30 September 1996. The station is in the lower ablation zone. Due to shading by surrounding mountains and atmospheric attenuation, only 49% of the annual extraterrestrial irradiance (mean: 292 W m−2) reaches the glacier surface. About 48% of this is absorbed at the surface (mean: 79 W m−2; annual albedo of 0.53).

We present a simple albedo scheme for use in glacier mass-balance models. We fit the model to the 1 year dataset by optimizing five control parameters (optimal values in brackets): albedo of snow (0.75), albedo of firn (0.53), albedo of ice (0.34), e-folding constant for effect of ageing on snow albedo (21.9 days) and e-folding constant for effect of snow depth on albedo (3.2 cm). The input consists of daily albedo, snow depth and dates of snowfall events. The correlation coefficient between observed and simulated albedo is 0.931, the corresponding rms difference being 0.067.
Geometric evolution and ice dynamics during a surge of Bakaninbreen, Svalbard
Authors: Murray Tavi , Dowdeswell Julian A. , Drewry David J. , Frearson Ian
Published: September 2017

Bakaninbreen, Svalbard, started surging in 1985 and developed a steep surge front where fast-moving ice impinged on stagnant non-surging ice. This front, which was 20- 25 m high in 1985, became a steep and heavily crevassed feature about 60 m high. The surge continued through 1986-95. Annual surge-front propagation rate was 1.0 1.8 km a−1 during 1985-89; this rate dropped considerably during 1989 95 and the front became less steep. Front propagation occurred largely by longitudinal compression and vertical extension of the ice and the effects of over-riding appear minor. Ice velocities were slower than the average propagation rate of the front. The surge affected Bakaninbreen in four zones: (1) Upper region where extensive flow, fast propagation rates and negative vertical strain occurred, resulting in widespread crevassing and stranded blocks tens of metres above the post-surge ice surface, (2) Mid-glacier region where initial strong compression was associated with ice thickening which started before the arrivai of the surge front. Horizontal strain rates were very low but vertical strain rates were tip to 300 mmd−1. As (he front passed, the horizontal velocity increased and about 500 m behind it became extensive. Negative vertical strain and ice down-draw occurred as ice velocities dropped, (3) Surge front where ice velocity was high but vertical strain remained positive associated with compression. (4) Lower region below the iront where only compression occurred, resulting in the formation of a fore bulge, a thickening of the ice of up to 50 m above pre-surge levels. The fore bulge affected the whole 1.7 km below the, now halted, surge front. The glacier has not advanced, Bakaninbreen’s surge was characterized by a long active phase, approximately 10 years, low ice velocities and low basal shear stresses compared to glaciers in lower latitudes, and an indistinct surge termination.
Isotopic diffusion in polar firn: implications for interpretation of seasonal climate parameters in ice-core records, with emphasis on central Greenland
Authors: Cuffey Kurt M. , Steig Eric J.
Published: September 2017

If it were possible to properly extract seasonal information from ice-core isotopic records, paleoclimate researchers could retrieve a wealth of new information concerning the nature of climate changes and the meaning of trends observed in ice-core proxy records. It is widely recognized, however, that the diffusional smoothing of the seasonal record makes a “proper extraction" very difficult. In this paper, we examine the extent to which seasonal information (specifically the amplitude and shape of the seasonal cycle) is irrecoverably destroyed by diffusion in the firn. First, we show that isotopic diffusion firn is reasonably well understood. We do this by showing that a slightly modified version of the Whillans and Grootes (1985) theory makes a tenable a priori prediction of the decay of seasonal isotopic amplitudes with depth at the GISP2 site, though a small adjustment to one parameter significantly improves the prediction. Further, we calculate the amplitude decay at various other ice-core sites and show that these predictions compare favorably with published data from South Pole and locations in southern and central Greenland and the Antarctic Peninsula. We then present numerical experiments wherein synthetic ice-core records are created, diffused, sampled, reconstituted and compared to the original. These show that, alter diffusive mixing in the entire fini column, seasonal amplitudes can be reconstructed to within about 20% error in central Greenland but that all information about sub-annual signals is permanently lost there. Furthermore, most of the error in the amplitude reconstructions is due to the unknowable variations in the sub-annual signal. Finally, we explore how these results can be applied to other locations and suggest that Dye 3 has a high potential for meaningful seasonal reconstructions, while Siple Dome has no potential at all. An optimal ice-core site for seasonal reconstructions has a high accumulation rate and a low temperature.
The stability of a viscous till sheet coupled with ice flow, considered at wavelengths less than the ice thickness
Authors: Hindmarsh Richard C. A.
Published: September 2017

A perturbation method is used to analyse the stability of a thin till layer overlain by a deep ice layer. Ice is modelled as a linearly viscous fluid, while the till viscosity has power-law dependence on stress and effective pressure. A linearized set of equations yields descriptions of the coupling of the ice flow with the sediment flow and reveals parameter ranges where the till-perturbation amplitude can grow. This sheet-flow instability is an essential part of any theory of drumlin formation and shows that viscous models of till have the ability to explain typical deforming-bed features. This is of great significance for large-scale ice-sheet modelling.
Mass balance of glaciers other than the ice sheets
Authors: Cogley J. Graham , Adams W. P.
Published: September 2017

Small glaciers appear to have been at equilibrium or shrinking very slightly during 1961–90, according to analysis of an essentially complete set of published measurements. Simple calculations give an average annual mass balance of –195 ± 59 mm a−1 (water equivalent) but this is too low because of systematic errors. Neglect of internal accumulation is responsible for some tens of millimeters of underestimate. Uneven spatial coverage, with fewer measurements where mass balances are less negative, accounts for about 50 mm a−1 of underestimate. This figure derives from spatial interpolation based on global data on ice extent and on an analysis of correlations between balance time series. The correlogram shows exponential decay, the scale length being about 600 km. The largest bias is due to a newly detected dependence of mass balance on glacier size. Among the 231 measured glaciers, many are small and belong to a restricted size range in which balance is negative, but much of the small-glacier extent is accounted for by larger glaciers in a size range where balance is indistinguishable from zero. Correcting for this size bias increases the average balance to –35 ± 89 mm a−1. Inspection of time series for 1940–95 (251 glaciers) shows that mass balance was least negative during the 1960s, and has varied in broad agreement with Northern Hemisphere temperature anomalies; smaller small glaciers (A < 16 km2) appear to be more sensitive than larger small glaciers to changes in thermal forcing. The small-glacier contribution to sea-level rise implied by this assessment is only 0.06–0.32 mm a−1, consistent with glaciers in general making little or no contribution to sea-level change during 1961–90.
Short-term velocity and water-pressure variations down-glacier from a riegel, Storglaciären, Sweden
Authors: Hanson Brian , LeB. Hooke Roger , Grace Edmund M.
Published: September 2017

During the 1991 94 summer held seasons, time-correlated measure-merits of water pressure and surface speed were made over and down-glacier from a major riegel on Storglaciären, Sweden. Measurements were made at sub-hourly time-scales in order to discern details in the diurnal cycle. Large water-input events, typically associated with rain storms, produced coherent, lagged surface-velocity responses that could be understood in terms of till deformation or decoupling, and these have been discussed elsewhere. The consequences of smaller diurnal water-pressure events w ere more enigmatic, in that acceleration of ice flow generally preceded the onset of the local water-pressure rise. From consideration of these data and other work done on the hydrology of Storglaciären, we infer that the ice in this area is generally pushed from behind via a relaxation in extensional strain across the riegel. Hence, accelerations occur in response to increases in water pressure that occur up-glacier and that precede local water-pressure rises. In addition, following a period of large storm events, surface speeds became more spatially coherent and were in phase with the diurnal water-pressure cycle. This suggests that the large water-pressure events lead to a spatially more homogeneous subglacial drainage system. Sliding laws need to take into account such temporal changes in spatial coherence of the subglacial drainage system.
Comparison of a three-dimensional model for glacier flow with field data from Haut Glacier d’Arolla, Switzerland
Authors: Hubbard Alun , Blatter Heinz , Nienow Peter , Mair Douglas , Hubbard Bryn
Published: September 2017

A three-dimensional, finite-difference model based on a first-order solution of the ice-flow equations is applied to Haut Glacier d’Arolla, Switzerland. The numerical model successfully converges at horizontal resolutions down to 70 m, so a number of detailed comparisons with field data can be made. Modelled surface velocities with no basal sliding component are compared with surface velocities observed on the glacier over four different time periods. The best fit is achieved with over-winter surface velocities (R2 = 0.75) using a rate factor, A, in Glen’s flow law of 0.063 a−1 bar−3. Surface zones of maximum computed effective stress display a high level of coincidence with observed crevassing, the orientation of which is successfully predicted by the direction of the tensile component of the computed principal surface stress. Comparison of the relative magnitude and direction of computed principal stresses with principal strains measured at the ice surface also correspond closely. In an attempt to simulate the observed annual velocity distribution within a cross-section of the glacier tongue, we incorporate two basal-motion patterns into the model. By treating net annual ice motion as a time-weighted composite of three separate flow situations: normal sliding, enhanced sliding and no sliding, we are able to reproduce the key features of the observed cross-sectional ice and basal slip velocity distributions. These experiments indicate there may be substantial decoupling taking place along an elongated narrow zone at the bed of Haut Glacier d’Arolla and that this decoupling interacts in a complex manner with the englacial stress and strain field.
Site information and initial results from deep ice drilling on Law Dome, Antarctica
Authors: Morgan V.I. , Wookey C.W. , Li J. , van Ommen T.D. , Skinner W. , Fitzpatrick Μ.F.
Published: September 2017

The aim of deep ice drilling on Law Dome, Antarctica, has been to exploit the special characteristics of Law Dome summit, i.e. low temperature and high accumulation near an ice divide, to obtain a high-resolution ice core for climatic/environmental studies of the Holocene and the Last Glacial Maximum (LGM). Drilling was completed in February 1993, when basal ice containing small fragments of rock was reached at a depth of 1196 m. Accurate ice dating, obtained by counting annual layers revealed by fine-detail δ18О, peroxide and electrical-conductivity measurements, is continuous down to 399 m, corresponding to a date of AD 1304. Sulphate concentration measurements, made around depths where conductivity tracing indicates volcanic fallout, allow confirmation of the dating (for Agung in 1963 and Tambora in 1815) or estimates of the eruption date from the ice dating (for the Kuwae, Vanuatu, eruption ~1457). The lower part of the core is dated by extrapolating the layer-counting using a simple model of the ice flow. At the LGM, ice-fabric measurements show a large decrease (250 to 14 mm2) in crystal size and a narrow maximum in c-axis vertically. The main zone of strong single-pole fabrics however, is located higher up in a broad zone around 900 m. Oxygen-isotope (δ18O) measurements show Holocene ice down to 1113 m, the LGM at 1133 m and warm (δ18O) about the same as Holocene) ice near the base of the ice sheet. The LGM/Holocene δ18O shift of 7.0‰, only ~1‰ larger than for Vostok, indicates that Law Dome remained an independent ice cap and was not overridden by the inland ice sheet in the Glacial.
Response of the longwave radiation over melting snow and ice to atmospheric warming
Authors: Meesters Antoon , van den Broeke Michiel
Published: September 2017

Parameterizing the incoming longwave radiation L ↓ in terms of the fourth power of the absolute temperature at the reference height is used in glaciology for several purposes. In this paper, the validity of this kind of parameterization is investigated for the Greenland ice sheer, both by observations and by numerical simulation with a meso-scale model, It is found that such a parameterization severely underestimates the increase of L ↓ in response to large-scale warming in an area where surface melting is important. This is explained by the systematic influence that is exerted on the shape of the temperature profiles by surface melting.
Seasonal variations in the properties and structural composition of sea ice and snow cover in the Bellingshausen and Amundsen Seas, Antarctica
Authors: Jeffries M. O. , Morris K. , Weeks W.F. , Worby A. P.
Published: September 2017

Sixty-three ice cores were collected in the Bellingshausen and Amundsen Seas in August and September 1993 during a cruise of the R.V. Nathaniel B. Palmer. The structure and stable-isotopic composition (18O/16O) of the cores were investigated in order to understand the growth conditions and to identify the key growth processes, particularly the contribution of snow to sea-ice formation. The structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the Bellingshausen Sea in March 1992 are reassessed. Frazil ice and congelation ice contribute 44% and 26%, respectively, to the composition of both the winter and summer ice-core sets, evidence that the relatively calm conditions that favour congelation-ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil-ice growth and pancake-ice formation. Both frazil- and congelation-ice layers have an av erage thickness of 0.12 m in winter, evidence that congelation ice and pancake ice thicken primarily by dynamic processes. The thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover. Snow-ice layers have a mean thickness of 0.20 and 0.28 m in the winter and summer cores, respectively, and the contribution of snow ice to the winter (24%) and summer (16%) core sets exceeds most quantities that have been reported previously in other Antarctic pack-ice zones. The thickness and quantity of snow ice may be due to a combination of high snow-accumulation rates and snow loads, environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow/ice interface, and bottom melting losses being compensated by snow-ice formation. Layers of superimposed ice at the top of each of the summer cores make up 4.6% of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice. The accumulation of superimposed ice is evidence that melting in the snow cover on Antarctic sea-ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass.
The Dominion Range Ice Core, Queen Maud Mountains, Antarctica - General Site and Core Characteristics with Implications
Authors: Mayewski Paul A. , Twickler Mark S. , Lyons Wm Berry , Spencer Mary Jo , Meese Debra A. , Gow Anthony J. , Grootes Pieter , Sowers Todd , Watson M.Scott , Saltzman Eric
Published: September 2017

The Transantarctic Mountains of East Antarctica provide a new milieu for retrieval of ice-core records. We report here on the initial findings from the first of these records, the Dominion Range ice-core record. Sites such as the Dominion Range are valuable for the recovery of records detailing climate change, volcanic activity, and changes in the chemistry of the atmosphere. The unique geographic location of this site and a relatively low accumulation rate combine to provide a relatively long record of change for this potentially sensitive climatic region. As such, information concerning the site and general core characteristics are presented, including ice surface, ice thickness, bore-hole temperature, mean annual net accumulation, crystal size, crystal fabric, oxygen-isotope composition, and examples of ice chemistry and isotopic composition of trapped gases.
Icequakes On Ekström Ice Shelf Near Atka Bay, Antarctica
Authors: Osten-Woldenburg H. Von Der
Published: September 2017

Two seismic arrays recorded in an 11 month field experiment in 1985 the seismicity of Ekström Ice Shelf in the area of an ice rumple and an inlet, situated respectively about 10 km north-west and 7 km north of the German Antarctic station Georg von Neumayer (lat. 70°37′S., long. 08°22′W). Most of the focal depths of the icequakes considered until now are in the range 5–9 m; the ice-rumple area shows extremely high seismic activity. Tensile fracture is the most frequent fault mechanism, although there are a few shear-fracture events. The ice rumple’s seismicity provides information on the dynamics of the ice shelf in this area. A comparison of this time-dependent seismicity with tides suggests that most of this seismicity is induced by tides. The most active period of this seismicity starts at the beginning of low tide and ends at low tide. The location of the epicentres of icequakes recorded at that time and the digital recording on tapes of the seismicity without interruption for 396 h shows a jerky vertical movement of the ice shelf in response to tides; this can be interpreted as a kind of “grater effect”, especially at the southern ice-rock boundary of the ice rumple.

The seismicity in the inlet is much less and tensile fracture seems to be the only fault mechanism.
On the Numerical Solution of Stefan Problems in Temperate Ice
Authors: Hutter Kolumban , Zryd Amédé , Röthlisberger Hans
Published: September 2017

Freezing processes in temperate ice consisting of a mixture of pure ice with water inclusions are studied for the case that the initial amount of moisture content is uniform. By introducing a cold source at the center of the ice specimen, the cold front propagates outwards leaving behind pure cold ice with a temperature distribution dictated by the exact set-up of the cold source. The speed of the front is directly related to the water content of the temperate ice and depends essentially on the Stefan condition.

Three types of initial and boundary conditions are considered and realized in uniaxial, cylindrical, and/or spherical symmetry: (1) a metallic core at a temperature below the freezing point is initially brought into contact with the ice and the system is left free to evolve; (2) the metallic core is kept at constant temperature below freezing; (3) Case (2) is repeated with an insulating air layer between the metallic core and the ice.
Jakobshavns Isbræ, West Greenland: Seasonal Variations in Velocity - or Lack Thereof
Authors: Echelmeyer Keith , Harrison William D.
Published: September 2017

The lower 80 km of the fast-moving Jakobshavns Isbræ, West Greenland, is subject to significant melting during the summer season. The melt water drains into large supraglacial rivers which pour into moulins or feed into beautiful supraglacial lakes, some of which are observed to drain periodically. Except for a few streams that drain directly off the margins of the ice sheet within the drainage basin of this glacier, the fate of this melt water is unknown. However, a localized upwelling of highly turbid water is often observed during the melt season in the fjord adjacent Io the terminal cliff of the glacier, indicating that water from some source does move along the glacier bed.

As part of an investigation on the mechanisms of rapid flow on Jakobshavns Isbræ, measurements of surface velocity at several (∼25) locations along the ice stream at and below the equilibrium line were made in order to investigate the effects of this seasonally varying input of melt water on the speed of the glacier.

No significant seasonal variation in speed was found at any location. This indicates that, unlike many other sub-polar and temperate glaciers, surface melt-water production does not affect the motion of this glacier on a seasonal basis, and, thus, does not cause a significant temporal variation in basal sliding. This finding has important ramifications on the mechanisms of flow for this ice stream.
Configuration of the Drainage System of Midtdalsbreen, Norway, as Indicated by Dye-Tracing Experiments
Authors: Willis Ian C. , Sharp Martin J. , Richards Keith S.
Published: September 2017

During the summers of 1987 and 1988, 15 dye-tracer tests from a total of eight injection points were conducted in the ablation area of Midtdalsbreen, a northern outlet of Hardangerjokulen, southern Norway. The spatial and temporal patterns of water discharge, shapes of the dye-return curves, through-flow velocities, dye-recovery rates, dispersivities, and velocity/discharge relationships suggest the existence of distinct catchments beneath the eastern and western halves of the glacier which are characterized by different types of drainage sytem. Experiments on the eastern side were associated with high melt-water discharges and produced short-lived and highly peaked dye-return curves, fast through-flow velocities, high dye-recovery rates, low dispersivity values which decreased through the melt season, and a velocity/discharge relationship with an exponent of 1.0. Experiments on the western side were associated with low melt-water discharges and produced flat, extended dye-return curves which often displayed secondary peaks, slow through-flow velocities, low dye-recovery rates, high dispersivity values which increased during the melt season, and a velocity/discharge relationship with an exponent of 0.6. Comparison of observed through-flow velocities with values calculated theoretically using various hypothetical drainage-system structures suggests that water flows in a major sinuous conduit beneath the eastern half of the glacier and in a system of linked cavities beneath the western half. A model for the seasonal evolution of the whole drainage network is postulated which has important implications for temporal variations in subglacial water pressures and glacier-sliding velocity.