bluuebunny/crossref_metadata_2025 huggingface dataset:
A Prospective Study of Childhood Emotional and Behavioural Problems in Port Pirie, South Australia
Authors: Sawyer Michael G. , Mudge Jane , Carty Vanessa , Baghurst Peter , McMichael Anthony
Published: November 2007

Objective: To describe the extent to which emotional and behavioural problems experienced by 5-year-old children living in or around Port Pirie, South Australia, persisted when the children were aged 11–12 years. Method: Childhood emotional and behavioural problems were identified at the age of 5 years using Child Behaviour Checklists completed by mothers. When the children were aged 11–12 years, problems were identified using checklists completed by mothers, children and teachers.

Results: Attention problems, aggressive behaviour and anxious/depressed problems were the most persistent problems over this period of the children's lives. In general, the strongest relationship over time occurred when reports were obtained from mothers on each occasion. A weaker relationship existed between earlier mother-reported problems and later teacher-reported problems, while the relationship between mother-reported problems and later self-reported problems occupied an intermediate position.

Conclusion: The course of problems among children in Port Pirie appeared similar to that previously reported for children in Holland and North America. To better understand the aetiology of psychiatric disorders and to plan for effective interventions, more information is needed about the natural course of childhood emotional and behavioural disorders in Australia.
Assessing the Prevalence of Eating Disorders in an Australian Twin Population
Authors: Wade Tracey , Heath Andrew C. , Abraham Suzanne , Treloar Susan A. , Martin N. G. , Tiggemann M.
Published: November 2007

Objective: This paper examines the prevalence of disordered eating in a female Australian twin population aged between 28 and 90 years in 1993.

Method: In two waves of data collection, the eating behaviour of 3869 female twins was first assessed in 1988–1989 by self-report questionnaire and then in 1992-1993 with a telephone interview, using the Semi-Structured Assessment for the Genetics of Alcoholism interview.

Results: It was found that about 0.4% of the women have a lifetime prevalence of anorexia nervosa and 1.8% of the group have suffered from bulimia nervosa. The incidence of bulimia nervosa but not anorexia nervosa was markedly higher for those women under 45 (2.3% bulimia nervosa) than for those women 45 years or older. Furthermore, one in three women have at some stage in their life used some extreme method of weight control.

Conclusions: The levels of bulimia nervosa and anorexia nervosa found are commensurate with those found in smaller studies in Australia and other parts of the world. The finding of widespread use of extreme weight control methods is of concern as this behaviour is a well-recognised precursor to more serious eating disorders.
Lithium-Induced Neurotoxicity at Serum Lithium Levels within the Therapeutic Range
Authors: Arya Dinesh K.
Published: November 2007

Objective: To report the occurrence of lithium-induced neurotoxicity and extrapyramidal symptoms at serum lithium levels within the therapeutic range. Clinical picture: On two occasions, a 73-year-old patient presented with symptoms of lithium-induced neurotoxicity and extrapyramidal symptoms when her serum lithium levels were within the therapeutic range.

Treatment and outcome: Both lithium-induced neurotoxicity and extrapyramidal symptoms resolved when lithium was withdrawn.

Conclusion: Even when serum lithium levels are within the therapeutic range, lithium-induced neurotoxicity may occur. Patients on neuroleptics and the elderly in particular may be more vulnerable to these side effects.
Phobic Disorders are Associated with Temperament in Alcoholic Men
Authors: Sellman J. Douglas , Joyce Peter R.
Published: November 2007

Objective: To investigate whether in a sample of men with alcohol dependence those with comorbid phobic disorders had higher persistence scores than those without.

Method: Ninety-nine men with moderate–severe alcohol dependence recruited from an alcohol treatment programme were interviewed using the Structured Clinical Interview (SCID) and completed a Tridimensional Personality Questionnaire (TPQ).

Results: Subjects with a comorbid phobic disorder had significantly higher persistence scores compared to those without.

Conclusions: The temperament dimension, persistence, is associated with phobic disorder.
A Critique of ‘Organic’ and its Proposed Alternatives
Authors: Sachdev Perminder
Published: November 2007

Objective: A critical examination of the term ‘organic’ in psychiatry and its proposed alternatives.

Method: An examination of the published literature on the concepts of ‘organicity’ in mental syndromes, and of the mind-brain problem.

Results: The term ‘organic’ presents a number of problems, some of which can be described as those of historical schism, duality, method, practice, scholasticism and semantics. The currently available alternatives are not without their difficulties, and examples are provided.

Conclusion: Whether the term ‘organic’ is retained or replaced, we are condemned to an unsatisfactory position while we await a radically new paradigm to understand the role of neurobiological and psychosocial factors in psychiatric disorders.
Cannabis and the Brain
Authors: Castle David J. , Ames Frances R.
Published: November 2007

Objective: The aim of the paper is to review the effects of Cannabis sativa on the human brain.

Method: A selective literature review was undertaken.

Results/Conclusions: Cannabis sativa causes an acute and, with regular heavy ingestion, a subacute encephalopathy. There is no evidence of irreversible cerebral damage resulting from its use, although impairment of information processing might be a long-term consequence of heavy prolonged use. The precise relationship of cannabis to the functional psychoses such as schizophrenia has yet to be clarified.
What have We Learned from Functional Imaging Studies in Schizophrenia? the Role of Frontal, Striatal and Temporal Areas
Authors: Velakoulis Dennis , Pantelis Christos
Published: November 2007

Objectives: Functional imaging technologies allow assessment of cerebral blood flow, cerebral metabolism, cellular metabolic processes, cerebral receptor density and occupancy. This review examines the contribution of such studies to our understanding of schizophrenia. The role of the frontal lobes, the basal ganglia, the temporal lobes and the neuronal circuits which connect them is examined with respect to this literature.

Method: All studies in schizophrenia using positron emission tomography, single photon emission computerised tomography, xenon studies, functional and spectroscopic magnetic resonance imaging formed the basis of this review. Only those studies published in English were reviewed.

Results: The most consistent finding in schizophrenia has been that of hypofrontality, while the results of studies examining subcortical structures provide preliminary support for the concept of fronto-striatal dysfunction. Functional imaging has not yet provided consistent results in the study of temporal lobe function. Although receptor studies have shed light on the actions of antipsychotic medications, the findings for dopamine receptor numbers remain controversial. Spectroscopic and functional MRI remain in their infancy as research tools in schizophrenia.

Conclusions: Although there are significant methodological issues to be addressed, functional imaging technology is providing increasing insights into schizophrenia and its treatment. Future research will be truly multidisciplinary as it will require the collaboration of psychiatrists, imaging physicians, neuropsychologists and neuroscientists.
Season of Birth and Schizophrenia: Southern Hemisphere Data
Authors: Berk Michael , Terre-Blanche Martin John , Maude Catherine , Lucas Marilyn Doreen , Mendelsohn Michaela , O'neill-Kerr Alexander James
Published: November 2007

Objective: The association between winter birth and increased incidence of schizophrenia is well documented in the northern hemisphere. The present study examined season of birth and schizophrenia in a southern hemisphere population from a mild temperate climate.

Method: The seasonal incidence of birth in schizophrenic patients was compared, using Chi-squared tests, to normative population birth rates. Results: A statistically significant seasonal pattern, with a peak in late spring and early summer, was obtained.

Conclusion: This supports northern hemisphere findings regarding calendar month, but not season, of excess schizophrenic births. This has implications for viral and other aetiological hypotheses dependent on meteorological factors.
Consultation-Liaison Psychiatry to Renal Medicine: Work with an Inpatient Unit
Authors: Rustomjee Sabar , Smith Graeme C.
Published: November 2007

Objective: To provide an overview of the work of a liaison psychiatry service to a renal medicine inpatient unit, based on a comprehensive clinical database, in order to provide a basis for comparison with similar units and to identify issues of concern.

Method: The MICRO-CARES prospective clinical database system was used to obtain data on all patients referred to the Liaison Psychiatry Service, and the hospital clinical database was used to compare referred patients with total Renal Unit admissions in a large, suburban, university-affiliated hospital.

Results: Two hundred and ninety-nine inpatient referrals were made in the three years from 1990 to 1992: a referral rate of 17%. There was no bias in referral on age, sex or marital status. Coping problems (27%), depression (20%) and noncompliance (11%) were the most frequent reasons cited. Forty-five per cent of referrals required a pre-dialysis assessment. There was good agreement between consultee and consultant about noncompliance, but poorer agreement about organic brain syndromes, depression, anxiety and alcohol problems. The highest prevalence of DSM-III-R diagnoses was for V Codes (35% of patients), Adjustment Disorders (30%), Mood Disorders (24%) and Organic Mental Disorders (23%). Referred patients had a length of stay significantly longer than that of the total admissions (20.5 days ± 20.6 SD compared with 8.7 ± 12.5 SD, p<.001). Psychotropic drugs were prescribed in 25% of referrals, and liaison psychiatry staff spent a mean of 181 ±148 SD minutes per patient, reflecting the emphasis on psychological management. The systems issues are discussed.

Conclusions: The high level of complex physical/psychiatric comorbidity present and the systemic issues involved suggest that the management of patients in a renal medicine inpatient unit requires a dedicated attachment of a consultant psychiatrist-led, multidisciplinary, liaison psychiatry team which is well trained in psychodynamic issues and is comfortable with the complexity of biological issues which arise. The data provide a reliable basis for comparison with other services.
Photophobia and Lithium
Authors: Pridmore Saxby , Powell Geoffrey , Wise Gordon
Published: November 2007

Clinical picture: We report the case of a 45 year old woman who developed photophobia after 6 months on lithium at non-toxic levels.

Treatment and Outcome: Lithium was reintroduced twice and on both occasions this side-effect reoccurred within days.

Conclusions: Photophobia has only been described previously as a symptom of lithium intoxication.
Psychogenic Vomiting Complicated by Marijuana Abuse and Spontaneous Pneumomediastinum
Authors: de Moore Gregory M. , Baker John , Bui Triet
Published: November 2007

Objective: This case illustrates an unusual physical sequel of psychogenic vomiting.

Clinical picture: A 22-year-old man with a picture of psychogenic vomiting and marijuana use developed the complications of a pneumomediastinum and subcutaneous emphysema.

Treatment: Therapy included gradual exposure to anxiety provoking stimuli, psychotropics to reduce vomiting and psychotherapeutic exploration of family relationships.

Outcome: The patient's vomiting and physical state resolved without complication. Follow-up at 12 months revealed continued improvement with occasional less severe vomiting.

Conclusions: Psychogenic vomiting as a manifestation of anxiety can result in serious physical and psychological sequelae. This patient's desperate attempts to control such vomiting complicated the picture. Successful short term intervention included the use of several treatment modalities.
Practical Problems in the Use of the MECTA EEG Monitored ECT
Authors: White Brian , McMurray John , Rowland Danielle
Published: November 2007

The MECTA is an American made ECT machine which provides single channel EEG monitoring. This gives great improvement in the control of ECT. The Nepean Hospital Psychiatry Unit was opened in February 1991 and was equipped with a MECTA machine as well as the standard Kabronics machine. We found a range of practical difficulties and complications in commencing its use and with its continued use. There are limitations with the machine itself including the standard starter kit not being satisfactory regular use was not started until hand held paddles were obtained. The procedure is significantly more complex and time consuming, it requires more staffing input, it needs a more detailed knowledge base, and there are limitations on the EEG. There are some interesting empirical observations we can make about our results; any medication with anticonvulsant effect including the short acting benzodiazepines reduces the effectiveness of the ECT; and generally the EEG indicates a seizure continuing for half as long again as the observed modified fit. Overall, we are very pleased to be able to use EEG monitoring and in conjunction with our good quality oximeter provides a welcome high standard of safety and accuracy in the provision of ECT. This brief presentation will focus on the practical difficulties in the use of this machine and may be of assistance to others interested in EEG monitored ECT.
Anomie and Egoism in Relation to Contemporary Psychiatry
Authors: Spencer John
Published: November 2007

With increasing numbers of people in western society engaging in deliberate self-harm behaviours, psychiatric practitioners should reconsider some of the implications.

1. Psychiatry as a branch of medicine has a medical bias in assessing people who have engaged in deliberate self-harm behaviours and tends to view these behaviours as symptoms of psychiatric illness rather than sociological disorder.

2. The increasing number of these distressed people is causing an increasing psychiatric workload to the disadvantage of other patients, research activity and teaching.

3. The psychiatric profession should focus its attention on patients with formal psychiatric illness and encourage the involvement and participation of professionals from other agencies and services who are now trained and willing to become involved.

Psychiatry cannot replace the enfeebled phenomena of collective sentiment or the regulatory function of a simpler, more cohesive society (as described by Durkheim) but many of the established self-help groups can help and links could be established with these agencies. To do this will require changes to established professional role boundaries and the loosening of medico-legal constraints which currently prevent relinquishing of responsibility when there is an obvious absence of psychiatric illness.
The Practice of Psychiatry and Confusion of Roles
Authors: Ellard John
Published: November 2007

In Performing Their Ordinary Duties psychiatrists cannot avoid assuming a number of roles. More than that, if they venture into such fields as military, correctional or forensic psychiatry the roles multiply and so do the possibilities of confusion, with consequent error. It is not a fascinating topic but an important one, for many people can suffer when things go wrong—including the psychiatrist.
Insight, Acceptance, Management
Authors: Tony A.
Published: November 2007

In The Effort To Accept The Along term implications of psychiatric illness in my life I have compiled the following. It represents a series of journal entries over the period 25 February to 28 March 1995. The aim is to express the journey of illness and personal growth in my life in terms which could be understood by those others who may be battling similar circumstances.
Primary results of glaciological studies along an 1100 km transect from Zhongshan station to Dome A, East Antarctic ice sheet
Authors: Dahe Qin , Jiawen Ren , Jiancheng Kang , Cunde Xiao , Zhongqin Li , Yuansheng Li , Bo Sun , Weizhen Sun , Xiaoxiang Wang
Published: November 2007

The Chinese National Antarctic Research Expedition (GHINARE) carried out three traverses from Zhongshan station to Dome A, Princess Elizabeth Land and Inaccessible Area, East Antarctic ice sheet, during the 1996/97 to 1998/99 Antarctic field seasons. The expeditions are part of the Chinese International Trans-Antarctic Scientific Expedition program. In this project, glaciological investigations of mass balance, ice temperature, ice flow, stratigraphy in snow pits and snow/firn ice cores, as well as the glaciochemical study of surface snow and shallow ice cores, have been carried out. In the 1998/99 field season, CHINARE extended the traverse route to 1128 km inland from Zhongshan station. The density profiles show that firnification over Princess Elizabeth Land and Inaccessible Area (290–1100 km along the route) is fairly slow, and the accumulation rate recovered from snow pits along the initial 460 km of the route is 4.6–21 cm (46–210 kg m–2a–1 ) water equivalent. The initial 460 km of the route can be divided into four sections based on the differences of accumulation rate. This pattern approximately coincides with the study on the Lambert Glacier basin (LGB) by Australian scientists. During the past 50 years, the trends of both air temperature and accumulation rate show a slight increase in this area, in contrast to the west side of the LGB. Data on surface accumulation rates and their spatial and temporal variability over ice-drainage areas such as the LGB are essential for precise mass-balance calculation of the whole ice sheet, and are important for driving ice-sheet models and testing atmospheric models.
Verification of simulated snow cover in an Arctic basin using satellite-derived snow-cover maps
Authors: Turpin O. C. , Caves R. G. , Ferguson R. I. , Johansson B.
Published: November 2007

Time series of Earth observation (EO) data (Landsat Thematic Mapper (TM), U.S. National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA AVHRR) and European Remote-sensing Satellite synthetic-aperture radar (ERS SAR)) were obtained for a 2250 km2 mountainous basin in northern Sweden to validate snow-cover area (SCA) estimates produced by a conceptual model (HBV) during three melt seasons. SCA depletion curves derived for each image type, arid coincident images, reveal that the SCA estimate varies with the sensor. Discrepancies betweenTM and AVHRR appear to be an effect of spatial resolution. However, differences betweenTM and SAR are not simply related. Since more AVHRR thanTM data were available, a TM-equivalent SCA was derived from AVHRR by relating TM SCA to AVHRR channel 1 reflectance. The TM-equivalent SCA was used to test SCA simulated by HBV for the 1992 melt season. Although the modelled and TM-equivalent SCA were in reasonable agreement, the modelled SCA declined faster than the TM-equivalent SCA. Partial recalibration of model parameters controlling snowpack accumulation improved the match between the modelled and EO-derived SCA decline. The recalibrated parameters were verified using SCA maps generated for the 1996 and 1998 melt seasons. The adjusted parameter sets had little effect on the Nash-Sutcliffe R2 runoff fit but improved the volume fit in all three years.
Tributaries to West Antarctic ice streams: characteristics deduced from numerical modelling of ice flow
Authors: Hulbe Christina L. , Joughin Ian R. , Morse David L. , Bindschadler Robert A.
Published: November 2007

A network of relatively fast-flowing tributaries in the catchment basins of the West Antarctic ice streams transport ice from the inland reservoir to the heads of the ice streams. Branches of the network follow valleys in basal topography but not all valleys contain tributaries. We investigate the circumstances favoring tributary flow upstream of Ice Streams D and E, using a combination of observation and numerical modelling. No consistent pattern emerges. The transition from tributary to ice-stream flow occurs smoothly along the main tributary feeding into the onset of Ice Stream D, with ice thickness being relatively more important upstream, and sliding being relatively more important downstream. Elsewhere, the downstream pattern of flow is more complicated, with local increases and decreases in the contribution of sliding to ice speed. Those changes may be due to variations in basal water storage, subglacial geologic properties or a combination of the two.
Seasonal differences in surface energy exchange and accumulation at Summit, Greenland
Authors: Albert Mary R. , Hawley Robert L.
Published: November 2007

The 1997–98 Summit (Greenland) winter-over experiment was conducted to investigate the seasonal changes that might affect snow-air transfer processes and snow chemistry for polar ice-core interpretation This paper discusses meteorological measurements that were obtained during the experiment We use the measurements in energy-balance modeling to investigate seasonal differences in the snow-air energy exchange, and to investigate the timing of snow accumulation. We found that the surface energy exchange has distinct seasonal differences. The winter (November-February) has both the coldest average temperatures of the year and the largest temperature variations. The winter also has both the largest peak wind speeds and the longest periods of sustained high winds. Most of the water-vapor transport across the snow-air interface occurs in the summer, indicating that summer may be the primary season for near-surface snow metamorphism. Snow-depth sounder results indicate that snowfall occurs throughout the year at Summit, and thus that the ice-core record may not be affected by large seasonal gaps in the precipitation if accumulation patterns have not changed. The changes in air temperature, wind speed and radiation cause clear seasonal differences in the surface energy balance and snow-surface characteristics that are likely to cause seasonal changes in air-snow transfer processes and snow chemistry as well.
Remote-sensing science and technology for studying glacier processes in high Asia
Authors: Bishop Michael P. , Kargel Jeffrey S. , Kieffer Hugh H. , MacKinnon David J. , Raup Bruce H. , Shroder John F.
Published: November 2007

A large number of multispectral and stereo-image data are expected to become available as part of the Global Land Ice Measurements from Space project. We investigate digital elevation model extraction, anisotropic reflectance correction and selected glacier analysis tasks that must be developed to achieve full utility of these new data. Results indicate that glaciers in the Karakoram and Nanga Parbat Himalaya, northern Pakistan, exhibit unique spectral, spatial and geomorphometric patterns that can be exploited by various models and algorithms to produce accurate information regarding glacier extent, supraglacial features and glacier geomorphology The integration of spectral, spatial and geomorphometric features, coupled with approaches for advanced pattern recognition, can help geoscientists study glacier mass balance, glacier erosion, sediment-transfer efficiency and landscape evolution.
High-resolution measurements of spatial and temporal variations in surface velocities of Unteraargletscher, Bernese Alps, Switzerland
Authors: Gudmundsson G. H. , Bassi A. , Vonmoos M. , Bauder A. , Fischer U. H. , Funk M.
Published: November 2007

Data from automated in situ measurements of surface displacements on Unteraargletscher, Bernese Alps, Switzerland, made a few times a day from late June until late October 1998 are presented. Two short-term speed-up events were observed, and partial evidence for a third motion event was seen. Short-term motion events are thus not limited to the start of the melting season. Strong correlation between the timing of the motion events and periods of heavy rainfall, in conjunction with the large size of the area of the glacier which becomes activated during the events, both point towards an external triggering mechanism. In the time periods between two motion events, surface velocities do not vary significantly with time. After a motion event, surface velocities do not return to previous values, suggesting that the events have a lasting effect on the structure of the subglacial drainage system.
Modelling seasonal and spatial variations in the surface energy balance of Haut Glacier d’Arolla, Switzerland
Authors: Brock Ben W. , Willis Ian C. , Sharp Martin J. , Arnold Neil S.
Published: November 2007

The impact of spatial and temporal variations in the surface albedo and aerodynamic roughness length on the surface energy balance of Haut Glacier d’Arolla, Switzerland, was examined using a semi-distributed surface energy-balance model (Arnold and others, 1996). The model was updated to incorporate the glacier-wide effects of albedo and aerodynamic roughness-length variations using parameterizations following Brock (1997). After the model’s performance was validated, the glacier-wide patterns of the net shortwave, turbulent and melt energy fluxes were examined on four days, representative of surface conditions in late May, June July and August. In the model, meteorological conditions were held constant on each day in order that the impact of albedo and aerodynamic roughness-length variations could be assessed independently. A late-summer snowfall event was also simulated. Albedo and aerodynamic roughness-length variations, particularly those associated with the migration of the transient snowline and the decay of the winter snowpack, were found to exert a strong influence on the magnitude of the surface energy fluxes The importance of meteorological conditions in suppressing the surface energy fluxes and melt rate following a fresh snowfall was highlighted
Snow and firn permeability at Siple Dome, Antarctica
Authors: Albert Mary R. , Shultz Edward F. , Perron Frank E.
Published: November 2007

The nature of air-snow exchange processes depends upon both the physical characteristics of the snow and forcing from the atmosphere. An understanding of snow-air transport processes and models of these processes are important for interpreting ice cores and for predicting remotely sensed snow-surface characteristics. Accurate modeling requires knowledge of the physical characteristics of the snow and firn. In this paper, measurements of snow and firn permeability from the surface down to 12 m depth at Siple Dome, Antarctica, are presented. The permeability varies greatly as a function of layer and depth, generally increasing to approximately 3 m, and generally decreasing below that. The maximum permeability,280 × 10–10 1 0 m2, occurs at approximately 3 m depth. The lowest permeability in the top 12 m of snow and firn, 10 × 10–10w m2, was measured in the surface wind pack/The measurements show that layering and microstructure have large effects on permeability A mathematical expression for the overall variation of permeability with depth is presented It is shown that snow density is a poor indicator of permeability Quantitative microscopy may be helpful in relating observed snow characteristics to permeability, and useful in modeling firnification and chemical-species transport.
Model of the influence of snow cover on soil freezing
Authors: Osokin N. I. , Samoylov R. S. , Sosnovskiy A.V. , Sokratov S. A. , Zhidkov V. A.
Published: November 2007

A mathematical model of snow-cover influence on soil freezing, taking into account the phase transition layer, water migration in soil, frost heave and ice-layer formation, has been developed. The modeled results are in good agreement with data observed in natural conditions. The influence of a possible delay between the time of negative temperature establishment in the air and the beginning of snow accumulation, and possible variations of the thermophysical properties of snow cover in the wide range previously reported were investigated by numerical experiments. It was found that the delay could change the frozen-soil depth up to 2–3 times, while different thermophysical characteristics of snow changed the resulting freezing depth 4–5 times.
Attenuation of solar radiation in Arctic snow: field observations and modelling
Authors: Gerland S. , Liston G. E. , winther J.-G. , Ørbæk J. B. , Ivanov B.V.
Published: November 2007

Solar radiation was measured above and in the snowpack on Svalbard using a spectroradiometer and a quantum meter measuring average photosynthetically active radiation (PAR). In order to specify the effect of melting on the snow’s radiation properties, all measurements were performed before and during the melt season in May and June 1997 and 1998. Along with the radiation measurements, physical and structural snow properties were logged in snow pits. A physically based model was used to simulate the penetration of radiation into the snow The model formulation accounts for the spectrally dependent interactions between the radiation and snow grains, and requires inputs of the incoming solar radiation spectrum and the vertical snow density and grain-size. The vertical radiation-flux profile was computed using a two-stream radiation approximation where the absorption and reflection coefficients are related to the surface albedo, solar spectrum, grain-size and number of grains per unit volume. In general, snow before the onset of melt attenuates solar radiation more than coarser-grained snow that has been exposed to melting conditions. Quantum-meter measurements of PAR before and during melt can be explained by model outputs using both constant and variable extinction coefficients. Spectroradiometer measurements at fixed depth levels showed, in addition, that impurities in the snow reduce its transparency and therefore have the opposite effect to aging.
An integrated modelling approach to understanding subglacial hydraulic release events
Authors: Flowers Gwenn E. , Clarke Garry K. C.
Published: November 2007

Outbursts of subglacial water from numerous alpine glaciers have been observed and documented. Such events tend to occur in spring and are thus attributed to an inability of the winter subglacial drainage system (characterized by high water pressure and low capacity) to accommodate a sudden and profuse influx of surface meltwater. Prior to a release event, bursts of glacier motion are common, and the release then precipitates the restoration of summer plumbing that damps or terminates surface acceleration. The events bear witness to the importance of interactions between surface melt, runoff, en-glacial water storage and internal routing, in addition to subglacial drainage morphology. Using a distributed numerical model to simultaneously solve surficial, englacial and subglacial water-transport equations, we investigate the role of these components in a hydro-mechanical event observed at Trapridge Glacier, YukonTerritory, Canada, in July 1990.
Retreat of mountain glaciers of northern Eurasia since the Little Ice Age maximum
Authors: Solomina Olga N.
Published: November 2007

Analysis of aerial photographs of about 1000 glaciers located in the mountain ranges of the former Soviet Union –Caucasus, Polar Urals, Pamir-Alay, Tien Shan, Altay, Kodar, Cherskiy range, Suntar-Khayata, Koryakskoye Nagorye, Kamchatka–shows that variations in the magnitude of glacier retreat since the Little Ice Age maximum are significant and probably connected to climatic continentality. On average, the scale of glacier shrinkage is much smaller in continental Siberia than in central Asia and along the Pacific margins.
Material update procedure for planar transient flow of ice with evolving anisotropy
Authors: Gödert Günter , Hutter Kolumban
Published: November 2007

A flow law for polar ice is derived, which takes into account the effect of deformation-induced anisotropy due to hexagonal single-crystal symmetry. Attention is focused on the main effect of crystal-lattice rotation. Existence of a continuous so-called orientation-distribution function ODF, for the crystals is assumed. With its help the microscale constitutive behaviour is transformed to the large-scale. This transformation is simplified by imposing different consistency conditions (CC) due to Voigt-Taylor (VT) and Sachs-Reuss(SR), respectively. Here we take the grain interaction into account by linearly combining the VTand the SR conditions, i.e. by one additional parameter determining the relative weight of the two. A coupled finite-element-finite-volume approach is used to account for fabric evolution at the ice-sheet scale. For different CC, VT and SR, an orientation update is derived for planar flow, which results in only three additional degrees of freedom at each finite-element integration point to account for orthotropic material symmetry. Computations for the GRIP-core data demonstrate that a better fit can be obtained than with VT or SR alone.
Plane ice-sheet flow with evolving orthotopic fabric
Authors: Staroszczyk R. , Morland L.W.
Published: November 2007

A plane, gravity-driven, steady flow of an isothermal ice sheet over a horizontal bedrock, with no-slip basal conditions, is considered. The ice is modelled as a linearly viscous, incompressible and anisotropic fluid, with evolving orthotropic fabric that depends on local strain rates and deformations. For a fixed, free-surface elevation, the ice-accumulation rates necessary to maintain the prescribed geometry are calculated by using the finite-element method, together with the velocities and stresses. Numerical simulations have been carried out for different combinations of enhancement factors for compression and shear in order to investigate their effect on the rate of flow. The results obtained have shown that, apart from the near-divide region, the global flow rate is nearly proportional to the magnitude of the shear-enhancement factor and is very little sensitive to the value of the compression enhancement factor. Normalized velocity-depth profiles have been compared for the anisotropic and isotropic ice and it has been found that significant differences occur only in a region near the ice divide. Direct shear stresses are little affected by the ice anisotropy, but the longitudinal deviatoric stresses in a part of the ice sheet are significantly increased compared to the isotropic ice flow.
Large-scale force budget of an outlet glacier: Jutulstraumen, Dronning Maud Land, East Antarctica
Authors: Rolstad C. , Whillans I. M. , Hagen J. O. , Isaksson E.
Published: November 2007

A large-scale force budget was applied using a combination of remote-sensing and field data from Jutulstraumen, Dronning Maud Land, Antarctica. In the grounded area, more than 95 % of ice flow is balanced by basal friction. In a partly floating section near the grounding-line area, on average lateral drag provides 38% of resistance to flow.

Measurement uncertainties were propagated through the calculation of forces. The accuracies of strain rates derived from satellite data (Landsat thematic mapper) were found adequate to calculate meaningful force-balance terms. For the floating section, where lateral forces contribute to controlling flow, the main contribution to errors in the force budget is uncertainty in the rate factor for the flow law of ice. For grounded sections, the uncertainty in ice thickness, as measured by ground-penetrating radar, contributes more or less equally to errors in the force budget as does that in the rate factor.
Balance velocities and measured properties of the Antarctic ice sheet from a new compilation of gridded data for modelling
Authors: Huybrechts Philippe , Steinhage Daniel , Wilhelms Frank , Bamber Jonathan
Published: November 2007

This paper presents a new compilation of gridded datasets for three-dimensional modelling of the Antarctic ice sheet. These are for surface elevation, ice thickness, bedrock elevation and accumulation rate as interpolated on a 281 × 281 mesh with 20 km spacing, and encompass all the ice sheet and surrounding continental shelf. Data sources include the Bamber digital-elevation model from ERS-1 radar-altimeter data, a redigitization of available ice-thickness data, the Giovinetto accumulation data, recent ice-thickness data from British and German expeditions as well as accumulation data from German and Norwegian expeditions. In particular, new data were incorporated for the Filchner-Ronne Ice Shelf and for Dronning Maud Land, Antarctica, arising from the EPICA pre-site survey. Special attention was devoted to matching the various data sources carefully, both among themselves and across the grounding line and below the ice shelves, to enable ice-sheet expansion and retreat in dynamic situations. As an application, the balance flow is calculated over the entire ice sheet using a two-dimensional finite-difference scheme and compared with a previous assessment. This brought to light the existence of ice-streaming features extending well inland. A detailed zoom over Dronning Maud Land exhibits the general flow characteristics of interest for locating a future deep-drilling site. As a by-product, an updated value of 26.4 × 106km3 was obtained for the total volume of the ice sheet and ice shelves, or equivalent to 61.1 m of global sea-level rise after removal of the ice sheet and subsequent oceanic invasion and isostatic rebound. The total accumulation over the grounded ice sheet, including the Antarctic Peninsula, is 1924 Gta−1, or between 5 and 20% higher than earlier estimates. Including all the ice shelves, the value is 2344 Gt a−1.
Laurentide ice sheet aspect ratio in models based on Glen’s flow law
Authors: Tarasov Lev , Peltier W. Richard
Published: November 2007

The problem of recovering the small aspect ratio of the ICE-4G reconstruction of the Last Glacial Maximum Laurentide ice sheet has proven to be a challenge for state-of-the-art thermomechanically-coupled three-dimensional ice-sheet models coupled to reduced climate models. Flow enhancements to Glen’s flow law, 20 to 30 times those required to adequately simulate the present-day Greenland ice sheet, have been found necessary in order to reproduce both the thickness and areal extent of the geophysical reconstruction. Within the confines of the Glen flow rheology, it is unclear what mechanism might explain the magnitude of this discrepancy in required flow enhancement for the Laurentide relative to the Greenland ice sheet We present a comparative analysis of three alternative explanations of such a questionable flow-law enhancement: radical changes to mass balance; radical changes to ice-sheet history; and strongly enhanced basal flows Based on this analysis, we argue that none of these alternatives provide a fully acceptable explanation for the small ICE-4G LGM aspect ratio of the Laurentide ice sheet, that has been inferred geophysically.
Sliding over anisotropic beds
Authors: Hindmarsh Richard C.A.
Published: November 2007

Many glacier beds are anisotropic, by which is meant that the dominant wavelengths are different in the two map-plane directions. A largely unexplored consequence of Nye-Kamb sliding theory is the fact that an anisotropic bed can produce a sliding velocity not parallel to the tangential traction vector. This has important consequences, since observations of non-parallel flow are often taken as indications that the shallow-ice approximation has broken down, whereas this need not be the case with an anisotropic bed.

Mathematically, this effect can be incorporated through the use of a sliding tensor. The mathematical properties of this tensor are outlined, and the correct "invariant" for the sliding law, a quadratic form, is deduced. Nye-Kamb theory for anisotropic beds is discussed. Flow on the infinite plane and the properties of surface-topography diffusion are elucidated. The properties of kinematic waves and shock waves are discussed. Kinematic waves can have a lateral component. Numerical computations of ice-sheet flow on beds with anisotropic roughness are presented, with emphasis placed on how this affects divide-ridge structure It is suggested that cold-based ice sheets, which have an anisotropic bed affecting the shear layer, may also show non-parallelism of surface slope and velocity.
Influence of geometrical boundary conditions on the estimation of rheological parameters
Authors: Testut L. , Tabacco I. E. , Bianchi C. , Rémy F.
Published: November 2007

Improved knowledge of geometrical boundary conditions, such as bedrock geometry and surface topography, can contribute significantly to glaciological studies including ice-sheet-flow modelling. Precise thickness and altimetric data allow an estimation of ice-flow direction, the balance velocity and the basal shear stress. These parameters are calculated along a 1160 km profile in East Antarctica using a relationship between shear stress, basal temperature, the Glen flow exponent and a parameter related to strain rate. Strong variations of the flow-law parameters and basal conditions are found to play a major role in the ice-flow pattern. Sliding, anisotropy and longitudinal stress strongly perturb the validity of the law, but their signature can be identified.
Seasonal development of the sea-ice thickness distribution in East Antarctica: measurements from upward-looking sonar
Authors: Worby A. P. , Bush G. M. , Allison I.
Published: November 2007

Upward-looking sonar (ULS) data are presented from a prototype instrument deployed at 63° 18’ S, 107°49’ E in 1994. These data show the seasonal evolution of the ice-draft distribution from May when predominantly thin ice is present, through October when substantially thicker ice has been formed by deformation. The mean ice draft reaches a maximum in August at 1.21 m, the same month in which ship-based observations from the same region show a peak in ice thickness. The observed distribution from ULS data is only for drafts > 0.3 m due to data losses caused by the low acoustic reflectivity of actively forming ice. The spring distributions show very little development of drafts > 3.0 m, and it is hypothesized that this is due to the cyclical nature of deformation in the East Antarctic pack-ice zone, and that periods of sustained pressure required to form very thick ice are uncommon in this region
Sea-ice growth and water-mass modification in the Mertz Glacier polynya, East Antarctica, during winter
Authors: Bindoff N. L. , Williams G. D. , Allison I.
Published: November 2007

In July-September 1999, an extensive oceanographic survey (87 conductivity-, temperature-and depth-measuring stations) was conducted in the Mertz Glacier polynya over the Adélie Depression off the Antarctic coast between 145° and 150° E. We identify and describe four key water masses in this polynya: highly modified circumpolar deep water (HMCDW), winter water (WW), ice-shelf water (ISW) and high-salinity shelf water (HSSW). Combining surface velocity data (from an acoustic Doppler current-profiler) with three hydrographic sections, we found the HMCDW to be flowing westward along the shelf break (0.7 Sv), the WW and HSSW flowing eastwards underneath Mertz Glacier (2.0 Sv) and that there was a westward return flow of ISW against the continent (1.2 Sv). Using a simple box model for the exchanges of heat and fresh water between the principal water masses, we find that the polynya was primarily a latent-heat polynya with 95% of the total heat flux caused by sea-ice formation. This heat flux results from a fresh-water-equivalent sea-ice growth rate of 4.9−7.7 cm d−1 and a mass exchange between HMCDW and WW of 1.45 Sv The inferred ocean heat flux is 8−14 W m−2 and compares well with other indirect estimates.
Chlorinity/salinity distribution patterns in experimental granular sea ice
Authors: Tison J.-L. , Verbeke V.
Published: November 2007

This work investigates the possibility of brine-channel formation and development during the freezing of granular ice from a loose frazil-ice suspension in an NaCl solution at set-water concentration. Three experiments were performed at various constant growth rates in a purpose-built vessel with computer-controlled thermal driving. High-resolution chlorinity measurements are used as a proxy for the bulk salinity of the samples. These show clear brine-segregation processes in the ice, with very high salinity gradients for the fast (10 mm h−1) to medium (2 mm h−1) freezing rates, provided that a suitable sampling scale is adopted. Weak segregation was found at the low freezing rate (0.5 mm h−1). The spatial distribution of the bulk salinity fits the visual appearance of brine channels in the ice adequately, in both horizontal and vertical sections. In a similar way to columnar-congelation sea ice, the number of brine channels significantly decreases with growth rate, but the density of channels is systematically lower in the granular ice than that found at equivalent freezing rates in the columnar ice. This is attributed to the lower geometrical constraints on brine transport in the granular medium. Contrasts between brine-channel geometry and density at different growth rates are discussed in light of the "mushy-layer" concept adapted to sea-ice growth from the solidification of alloys
The surface energy budget in the Antarctic summer sea-ice pack
Authors: Wendler Gerd , Worby Anthony P.
Published: November 2007

The surface radiation budget was continuously measured in the sea-ice zone between 140° E (Terre Adélie) and 180° (McMurdo Sound) close to mid-summer, when the sea ice is disintegrating. These measurements were carried out during a cruise of the USCGC Polar Sea from Hobart, Tasmania, to McMurdo station, Antarctica, in 1998/99. Some of the findings are: the solar radiation is the major atmospheric energy source for the melting of ice. The sun was above the horizon for 24 h for most of the cruise. Due to a high amount of fractional cloudiness, the global radiation was somewhat reduced when compared to areas with lesser cloud cover Mean noon values were around 400 W m−2, while at midnight a value of 30 W m−2 was measured. Daily mean values of the net shortwave radiation varied widely, a function of the reflectivity of the surface, which is strongly dependent not only on the ice concentration, but also on the ice type (e.g. whether it is covered with snow, flooded, melting or dry). Detailed ice observations were carried out. Hourly values of the albedo varied from 6% (open water) to 84% (10/10 sea ice with a dry snow cover). The mean net longwave radiation was only modestly negative. The high amount of fractional cloud cover increased the longwave incoming radiation from the atmosphere. A mean value of −40 W m−2 was measured, which displayed only a very weak diurnal course. The sum of the short- and longwave radiation, the total radiation budget, showed the expected diurnal variation, with slightly negative values at night (for 6 h), and a mean maximum at solar noon of around 220 W m−2. A mean daily value of 98 W m−2 was calculated.