bluuebunny/crossref_metadata_2025 huggingface dataset:
Disorders of Glucose Regulation in Adults and Birth Weight
Authors: Al Salmi Isa , Hoy Wendy E. , Kondalsamy-Chennakesavan Srinivas , Wang Zhiqiang , Gobe Glenda C. , Barr Elizabeth L. M. , Shaw Jonathan E.
Published: December 2007

OBJECTIVE—The purpose of this study was to examine the association of birth weight with indexes of glycemia in a population-based survey.

RESEARCH DESIGN AND METHODS—A total of 10,788 participants in the Australian Diabetes, Obesity and Lifestyle (AusDiab) Study were asked to complete a birth weight questionnaire. Fasting plasma glucose (FPG), postload glucose (PLG), and A1C were modeled against birth weight. World Health Organization criteria were used to define impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetes.

RESULTS—Among 7,157 participants who responded to the questionnaire, 4,502 reported their birth weights, with a mean ± SD of 3.4 ± 0.7 kg. FPG, PLG, and A1C were strongly and inversely correlated with birth weight. The odds ratios (95% CI) for high (>90th sex-specific percentile) FPG, PLG, and A1C were 0.83 (0.71–0.96), 0.74 (0.65–0.84), and 0.81 (0.70–0.94), respectively, for a 1-kg increase in birth weight after adjustment for age and sex. In those with low birth weight (LBW), the risks for having IFG, IGT, and diabetes and for all abnormalities combined were increased by 1.75, 2.22, 2.76, and 2.28, respectively, for women and by 1.40, 1.32, 1.98, and 1.49 for men compared with risks for those with normal birth weight. These trends applied across categories of age and BMI.

CONCLUSIONS—In an affluent Western country with a good adult health profile, birth weight has an inverse relationship with indexes of glycemia, and individuals with LBW were predisposed to higher rates of glycemic dysregulation in adult life. These associations were independent of BMI and of other factors significantly correlated with glycemic dysregulation.
Reduction in Diabetic Amputations Over 11 Years in a Defined U.K. Population
Authors: Krishnan Singhan , Nash Fiona , Baker Neil , Fowler Duncan , Rayman Gerry
Published: December 2007

OBJECTIVE—To assess changes in diabetic lower-extremity amputation rates in a defined relatively static population over an 11-year period following the introduction of a multidisciplinary foot team.

RESEARCH DESIGN AND METHODS—All diabetic patients with foot problems admitted to Ipswich Hospital, a large district general hospital, were identified by twice-weekly surveillance of all relevant in-patient areas and outcomes including amputations recorded.

RESULTS—The incidence of major amputations fell 62%, from 7.4 to 2.8 per 100,000 of the general population. Total amputation rates also decreased (40.3%) but to a lesser extent due to a small increase in minor amputations. Expressed as incidence per 10,000 people with diabetes, total amputations fell 70%, from 53.2 to 16.0, and major amputations fell 82%, from 36.4 to 6.7.

CONCLUSIONS—Significant reductions in total and major amputation rates occurred over the 11-year period following improvements in foot care services including multidisciplinary team work.
Insulin Reduces Plasma Arginase Activity in Type 2 Diabetic Patients
Authors: Kashyap Sangeeta R. , Lara Abigail , Zhang Renliang , Park Young Mi , DeFronzo Ralph A.
Published: December 2007

OBJECTIVE—We sought to determine whether dysregulation of arginine metabolism is related to insulin resistance and underlies impaired nitric oxide (NO) generation in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS—We measured plasma arginase activity, arginine metabolites, and skeletal muscle NO synthase (NOS) activity in 12 type 2 diabetic and 10 age-/BMI-matched nondiabetic subjects before and following a 4-h euglycemic-hyperinsulinemic clamp with muscle biopsies. Arginine metabolites were determined by tandem mass spectroscopy. Arginase activity was determined by conversion of [14C] guanidoinoarginine to [14C] urea.

RESULTS—Glucose disposal (Rd) was reduced by 50% in diabetic versus control subjects. NOS activity was fourfold reduced in the diabetic group (107 ± 45 vs. 459 ± 100 pmol · min−1 · mg protein−1; P < 0.05) and failed to increase with insulin. Plasma arginase activity was increased by 50% in the diabetic versus control group (0.48 ± 0.11 vs. 0.32 ± 0.12 μmol · ml−1 · h−1; P < 0.05) and markedly declined in diabetic subjects with 4-h insulin infusion (to 0.13 ± 0.04 μmol · ml−1 · h−1 vs. basal; P < 0.05). In both groups collectively, plasma arginase activity correlated positively with fasting plasma glucose (R = 0.46, P < 0.05) and A1C levels (R = 0.51, P < 0.02) but not with Rd.

CONCLUSIONS—Plasma arginase activity is increased in type 2 diabetic subjects with impaired NOS activity, correlates with the degree of hyperglycemia, and is reduced by physiologic hyperinsulinemia. Elevated arginase activity may contribute to impaired NO generation in type 2 diabetes, and insulin may ameliorate this defect via reducing arginase activity.
Sex Disparities in Control and Treatment of Modifiable Cardiovascular Disease Risk Factors Among Patients With Diabetes
Authors: Ferrara Assiamira , Mangione Carol M. , Kim Catherine , Marrero David G. , Curb David , Stevens Mark , Selby Joseph V. ,   for the Translating Research Into Action for Diabetes (TRIAD) Study Group
Published: December 2007

OBJECTIVE—Cardiovascular disease (CVD) mortality has decreased in men but not in women with diabetes. We investigated whether sex differences in control and treatment of CVD risk factors might underlie this disparity.

RESEARCH DESIGN AND METHODS—We performed cross-sectional analyses from a cohort of patients with diabetes sampled from 10 U.S. managed care health plans. Study end points included not being in control for CVD risk factors (≥140 mmHg for systolic blood pressure [SBP], ≥3.35 mmol/l for LDL cholesterol, and ≥8.0% for A1C) and the intensity of medication management (number of medication classes) for patients not in control. Logistic regression models with random intercepts were used to adjust probabilities of control and management for demographics, clinical characteristics, and clustering within health plans.

RESULTS—There were 1,315 women and 1,575 men with a history of CVD and 3,415 women and 2,516 men without a history of CVD. Among patients with CVD, adjusted estimated probabilities for not being in control and risk differences varied significantly between men and women for SBP (men 41.2%, women 46.6%; risk difference −5.4% [95% CI −9.5 to −1.3]) and LDL cholesterol (men 22.4%, women 28.3%; risk difference −5.9% [−9.9 to −1.8]). There were no significant sex differences in intensity of medication management for patients not in control. In patients without CVD there were no significant differences in control or intensity of medication management.

CONCLUSIONS—In diabetic patients with CVD, poorer control of SBP and LDL cholesterol for women may contribute to the sex disparity in CVD mortality trends.
Determinants of Whole-Body Protein Metabolism in Subjects With and Without Type 2 Diabetes
Authors: Gougeon Réjeanne , Morais José A. , Chevalier Stéphanie , Pereira Sandra , Lamarche Marie , Marliss Errol B.
Published: December 2007

OBJECTIVE—Whole-body protein metabolism is abnormal in suboptimally controlled type 2 diabetes and obesity. We hypothesized that glycemia, insulin resistance, and waist circumference modulate these alterations in type 2 diabetes and, to a lesser extent, in individuals without type 2 diabetes.

RESEARCH DESIGN AND METHODS—In 88 lean and obese subjects without and 40 with type 2 diabetes on an inpatient protein-controlled isoenergetic diet for 7 days, whole-body protein turnover was measured using the fed-fasted 60-h oral 15N-glycine method. Nitrogen flux was determined from urinary 15N urea and protein synthesis, breakdown and net balance calculated. Indexes of diabetes control, resting energy expenditure (REE), and body composition were assessed.

RESULTS—Higher protein turnover in obese subjects was further increased, and net balance was lower in type 2 diabetes. Waist-to-hip ratio and ln homeostasis model assessment of insulin resistance (HOMA-IR) explained 40% of the variance in flux in type 2 diabetes; fat-free mass and lnHOMA-IR explained 62% in subjects without type 2 diabetes. Overall, fasting glucose explained 16% of the variance in net balance. In type 2 diabetes, net balance correlated negatively with fasting glucose in men and positively with hip circumference in women.

CONCLUSIONS—Kinetics of whole-body protein metabolism are elevated, and net balance is diminished in type 2 diabetes, independently of obesity. Elevated flux is associated with greater visceral adiposity, REE, and insulin resistance of glucose. In type 2 diabetic men, these alterations worsened with magnitude of hyperglycemia. In type 2 diabetic women, larger hip circumferences may protect against such alterations. Our findings suggest that dietary protein requirements may be greater in type 2 diabetes to offset a reduced net balance, aggravated as glycemia increases, especially in men.
Reevaluating the Way We Classify the Diabetic Foot
Authors: Lavery Lawrence A. , Peters Edgar J.G. , Williams Jayme R. , Murdoch Douglas P. , Hudson Amanda , Lavery David C.
Published: December 2007

OBJECTIVE—To separately evaluate peripheral arterial occlusive disease (PAOD) and foot ulcer and amputation history in a diabetic foot risk classification to predict foot complications.

RESEARCH DESIGN AND METHODS—We evaluated 1,666 diabetic patients for 27.2 ± 4.2 months. Patients underwent a detailed foot assessment and were followed at regular intervals. We used a modified version of the International Working Group on the Diabetic Foot's (IWGDF's) risk classification to assess complications during the follow-up period.

RESULTS—There were more ulcerations, infections, amputations, and hospitalizations as risk group increased (χ2 for trend P < 0.001). When risk category 2 (neuropathy and deformity and/or PAOD) was stratified by PAOD, there were more complications in PAOD patients (P < 0.01). When risk group 3 patients (ulceration or amputation history) were separately stratified, there were more complications in subjects with previous amputation (P < 0.01).

CONCLUSIONS—We propose a new risk classification that predicts future foot complications better than that currently used by the IWGDF.
Ten-Year Trends in Self-Rated Health Among Spanish Adults With Diabetes, 1993–2003
Authors: Jiménez-Garcia Rodrigo , Jiménez-Trujillo Isabel , Hernandez-Barrera Valentin , Carrasco-Garrido Pilar , Lopez Ana , Gil Angel
Published: December 2007

OBJECTIVE—Improving health-related quality of life among individuals with diabetes is a public health goal. This study sought to assess trends in self-rated “fair” and “poor” health among Spanish adults with diabetes and to identify factors associated with fair and poor health using data from all five National Health Surveys conducted from 1993 to 2003.

RESEARCH DESIGN AND METHODS—Poisson regression analysis was used to assess the trend in fair or poor health status during the period 1993–2003 and to compare prevalences between diabetes and nondiabetes sufferers.

RESULTS—The most relevant finding of this study is that, among Spanish adults with diabetes, prevalence of fair or poor heath is more than double that of individuals without diabetes and that overall prevalence did not vary during the decade 1993–2003 (71.2 to 70.5%). The variables associated with an increased risk of self-rated fair or poor health were as follows: age 54–64 years (odds ratio [OR] 1.5) or ≥65 years (2.1), presence of comorbidity (4.3), female sex (1.2), lower educational level (1.7), obesity (1.3), and no physical activity (1.6).

CONCLUSIONS—The lack of improvement in self-rated health among Spanish adults with diabetes calls for urgent implementation of health-promotion, prevention, and diabetes-management strategies aimed at enhancing the quality of life of such individuals.
The Dipeptidyl Peptidase-4 Inhibitor Vildagliptin Improves β-Cell Function and Insulin Sensitivity in Subjects With Impaired Fasting Glucose
Authors: Utzschneider Kristina M. , Tong Jenny , Montgomery Brenda , Udayasankar Jayalakshmi , Gerchman Fernando , Marcovina Santica M. , Watson Catherine E. , Ligueros-Saylan Monica A. , Foley James E. , Holst Jens J. , Deacon Carolyn F. , Kahn Steven E.
Published: December 2007

OBJECTIVE—To evaluate the effect of treatment with the dipeptidyl peptidase (DPP)-4 inhibitor vildagliptin on insulin sensitivity and β-cell function in subjects with impaired fasting glucose (IFG).

RESEARCH DESIGN AND METHODS—A total of 22 subjects with IFG (11 female and 11 male, mean ± SD age 59.6 ± 11.5 years) were treated orally with 100 mg vildagliptin once daily in a single-blind study. Subjects received placebo for 2 weeks (run-in) followed by vildagliptin for 6 weeks (treatment) and then placebo for 2 weeks (washout). A frequently sampled intravenous glucose tolerance test (FSIGT), followed by a 2-h meal tolerance test (MTT), was performed at 2, 8, and 10 weeks. From the FSIGT, the acute insulin response to glucose (AIRg) and insulin sensitivity index (SI) were determined and used to compute the disposition index (AIRg × SI) as a measure of β-cell function.

RESULTS—Fasting plasma glucose did not change after 6 weeks of vildagliptin treatment. With treatment, mean ± SEM AIRg increased from 224 ± 44 to 286 ± 52 pmol/l (P < 0.05), and SI improved from 2.8 ± 0.5 to 3.5 ± 0.5 × 10−5 · min−1 · pmol−1 · l (P < 0.01), resulting in an increase in the disposition index from 688 ± 180 to 1,164 ± 318 × 10−5/min (P < 0.05). These effects were not sustained after washout. During the MTT, the incremental area under the glucose curve was significantly decreased after treatment (240 ± 15 vs. 191 ± 14 mmol · l−1 · min−1; P = 0.002), but this effect was not sustained after washout.

CONCLUSIONS—The DPP-4 inhibitor vildagliptin improves insulin sensitivity and β-cell function, leading to improved postprandial glycemia in subjects with IFG, who are known to have β-cell dysfunction. Thus, vildagliptin may prevent progression to diabetes in high-risk subjects.
Five-Year Impact of a Continuous Quality Improvement Effort Implemented by a Network of Diabetes Outpatient Clinics
Authors:   Club Diabete Sicili@
Published: December 2007

OBJECTIVE—To evaluate the impact of a continuous quality improvement effort implemented by a network of diabetes outpatient clinics in Sicily, Italy.

RESEARCH DESIGN AND METHODS—Twenty-two clinics adopted the same electronic medical record system. Process and intermediate outcomes indicators were identified and software was developed, enabling the extraction of the information needed for the profiling of quality of care. Data were centrally analyzed anonymously every year, and results were discussed in meetings with the participants. The performances of the different centers were ranked against the “best performers,” and the reasons for variation were discussed.

RESULTS—From 2001 to 2005, a total of 26,782 patients aged ≥18 years have been seen in the participating clinics. Rates of monitoring of A1C, blood pressure, lipid profile, and microalbuminuria constantly increased over the years. The percentage of individuals with A1C values ≤7.0% increased by 16.6%, while the proportion of patients with blood pressure ≤130/85 mmHg increased by 10.7%. The percentage of individuals with LDL cholesterol levels <100 mg/dl had a marked increase from 19.4 to 44.1%. Rates of use of lipid-lowering drugs, antihypertensive drugs, and aspirin also substantially raised over the years.

CONCLUSIONS—We found a strong consistency between increasing rates of monitoring, increasing drug prescription, and better levels of intermediate outcomes. Despite the satisfactory achievements, a substantial room for improvement in the care of diabetes still persists.
Oral Glucose Tolerance Test: A Reliable Tool for Early Detection of Glucose Abnormalities in Patients With Acute Myocardial Infarction in Clinical Practice
Authors: Wallander Märit , Malmberg Klas , Norhammar Anna , Rydén Lars , Tenerz Åke
Published: December 2007

OBJECTIVE—Previously undetected glucose abnormalities are common in patients with acute myocardial infarction (AMI). We evaluated long-term reliability of early glucometabolic classification of patients with AMI by repeated oral glucose tolerance tests (OGTTs).

RESEARCH DESIGN AND METHODS—A glucometabolic OGTT-based classification was obtained in 122 patients by measuring capillary whole-blood glucose. The classification was performed on three occasions, before hospital discharge and 3 and 12 months thereafter.

RESULTS—At discharge, 34, 31, and 34% were classified as having normal glucose tolerance, impaired glucose tolerance (IGT), or type 2 diabetes, respectively, and 93% of all patients with type 2 diabetes were still classified with type 2 diabetes (n = 27) or IGT (n = 12) after 12 months. The agreements between the OGTTs at discharge and 3 and 12 months were κ = 0.35, P < 0.001, and κ = 0.43, P < 0.001, respectively.

CONCLUSIONS—The outcome of an OGTT performed in AMI patients at hospital discharge reliably informs on long-term glucometabolic state.
Reduced Vascular Endothelial Growth Factor Expression and Intra-Epidermal Nerve Fiber Loss in Human Diabetic Neuropathy
Authors: Quattrini Cristian , Jeziorska Maria , Boulton Andrew J.M. , Malik Rayaz A.
Published: December 2007

OBJECTIVE—To assess the relevance of vascular endothelial growth factor (VEGF) in the maintenance of peripheral nerve integrity in diabetic neuropathy we have assessed the expression of VEGF and intra-epidermal nerve fiber density (IENFD) in skin biopsy samples from diabetic patients.

RESEARCH DESIGN AND METHODS—Fifty-three diabetic patients and 12 nondiabetic control subjects underwent neurological evaluation, electrophysiology, quantitative sensory, and autonomic function testing. Dermal blood flow responses were evaluated with laser Doppler flowmetry. Skin biopsies were performed on the dorsum of the foot, and IENFD was quantified and compared with the expression of vascular endothelial growth factor A (VEGF-A), its receptor vascular endothelial growth factor receptor 2 (VEGFR-2), hypoxia-inducible factor 1α (HIF-1α), and microvessel density.

RESULTS—IENFD decreased progressively with increasing severity of diabetic neuropathy (P < 0.001). The dermal blood flow response to acetylcholine was reduced in diabetic patients with mild and moderate neuropathy (P < 0.01), and the intensity of staining for epidermal VEGF-A was significantly reduced in diabetic patients compared with control subjects (P < 0.01). Epidermal HIF-1α and VEGFR-2 expression did not differ between groups.

CONCLUSIONS—Progressive endothelial dysfunction, a reduction in VEGF expression, and loss of intra-epidermal nerve fibers occurs in the foot skin of diabetic patients with increasing neuropathic severity.
Effect of Cinnamon on Glucose Control and Lipid Parameters
Authors: Baker William L. , Gutierrez-Williams Gabriela , White C. Michael , Kluger Jeffrey , Coleman Craig I.
Published: December 2007

OBJECTIVE—To perform a meta-analysis of randomized controlled trials of cinnamon to better characterize its impact on glucose and plasma lipids.

RESEARCH DESIGN AND METHODS—A systematic literature search through July 2007 was conducted to identify randomized placebo-controlled trials of cinnamon that reported data on A1C, fasting blood glucose (FBG), or lipid parameters. The mean change in each study end point from baseline was treated as a continuous variable, and the weighted mean difference was calculated as the difference between the mean value in the treatment and control groups. A random-effects model was used.

RESULTS—Five prospective randomized controlled trials (n = 282) were identified. Upon meta-analysis, the use of cinnamon did not significantly alter A1C, FBG, or lipid parameters. Subgroup and sensitivity analyses did not significantly change the results.

CONCLUSIONS—Cinnamon does not appear to improve A1C, FBG, or lipid parameters in patients with type 1 or type 2 diabetes.
Climatic analysis of Sea-ice variability in the Canadian Arctic from operational charts, 1980–2004
Authors: Kinnard Christophe , Zdanowicz Christian M. , Fisher David A. , Alt Bea , Mccourt Steve
Published: December 2007

We present a complete climatic analysis of Sea-ice conditions in the Canadian Arctic based on digitized operational charts from the Canadian Ice Service for the period 1980–2004. The Seasonal climatology, Spatial variance and linear trends in total ice concentrations (CT) were calculated. The maximum reduction rate in CT was found in the Beaufort Sea (>24% decade–1) and in the Davis Strait/Labrador Sea region (>18% decade–1) during Spring and Summer. Empirical orthogonal function (EOF) analysis performed on monthly CT deviations yielded four Significant EOF modes explaining 32% of the total variance. The Spatial pattern, temporal behaviour and Seasonality of these four EOF modes are discussed and correlated with fields of Sea-level pressure, Surface winds, Surface air temperature and Sea-surface temperature monthly anomalies. These results point to the dominant influence of the North Atlantic Oscillation on CT decadal anomalies during the cold Season, while climate variability in the Pacific influences CT variations in the Beaufort Sea region during Spring–summer.
Direct measurements of turbulent momentum, heat and salt fluxes under landfast ice in the Baltic Sea
Authors: Uusikivi Jari , Ehn Jens , Granskog Mats A.
Published: December 2007

Measurements of under-ice turbulence were performed using an acoustic three-dimensional current meter with an attached fast-repetition temperature–conductivity sensor at two coastal areas in the Baltic Sea during two winters. Observations covered both the ice-growth and spring-melt periods. The objective of these measurements was to obtain knowledge of under-ice turbulence and oceanic heat and salt fluxes to and from the ice in the coastal fast-ice region using eddy correlation techniques. The maximum observed daily average heat flux was 1 Wm–2, and the maximum for 10 min periods was an order of magnitude larger. Under-ice turbulence was much smaller than that recorded in the oceans and in coastal regions with tide. These results provide better knowledge of under-ice turbulence and heat-flux variations and are useful for the future development of a Baltic Sea ice salinity model.
Modeling M2 tidal variability in Arctic Sea-ice drift and deformation
Authors: Hibler W.D. , Roberts A. , Heil P. , Proshutinsky A.Y. , Simmons H.L. , Lovick J.
Published: December 2007

Semi-diurnal oscillations are a ubiquitous feature of polar Sea-ice motion. Over much of the Arctic basin, inertial and Semi-diurnal tidal variability have Similar frequencies So that periodicity alone is inadequate to determine the Source of oscillations. We investigate the relative roles of tidal and inertial variability in Arctic Sea ice using a barotropic ice–ocean model with Sea ice embedded in an upper boundary layer. Results from this model are compared with ‘levitated’ ice–ocean coupling used in many models. In levitated models the mechanical buoyancy effect of Sea ice is neglected So that convergence of ice, for example, does not affect the oceanic Ekman flux. We use rotary Spectral analysis to compare Simulated and observed results. This helps to interpret the rotation Sense of Sea-ice drift and deformation at the Semi-diurnal period and is a useful discriminator between tidal and inertial effects. Results indicate that the levitated model generates an artificial inertial resonance in the presence of tidal and wind forcing, contrary to the embedded Sea-ice model. We conclude that Sea-ice mechanics can cause the rotational response of ice motion to change Sign even in the presence of Strong and opposing local tidal forcing when a physically consistent dynamic ice–ocean coupling is employed.
Data assimilation of Sea-ice motion vectors: Sensitivity to the parameterization of Sea-ice Strength
Authors: Dai Mingrui , Arbetter Todd E. , Meier Walter N.
Published: December 2007

Data assimilation techniques are one method by which to improve the quality of model Simulations of Sea ice. The availability of daily gridded fields of Sea-ice motion makes this field one that can be readily assimilated. These fields are generally of higher resolution than forcing values Such as atmospheric wind which are used to drive the model, and on any given day may depict ice circulation that is dramatically different than what the model Solution represents. Typically, a blending method Such as optimal interpolation (OI) is used and corrections are applied to the initial modeled velocity field Such that the new Solution corresponds better with actual observations. However, care must be taken in Such a technique, as the corrections are not applied directly to the model physics, and the underlying physical assumptions in the ice dynamics may be violated. Previous Studies have Shown that improvements in the ice-motion Solution come at the cost of the quality of other modeled fields. The Strength parameterization in Sea-ice models controls the ice velocity in the model, and is obtained in part by comparison with observed motions. Here we investigate the Sensitivity of the Sea-ice model to variations in the Strength parameterization, and determine the effect of using data assimilation to impose observed velocities. We find that the alternation of the frictional loss parameter has limited effect on model performance. Rather, it is the assimilated data that overwhelm and degrade the Solution, bringing into question whether underlying physical assumptions in the model may be compromised.
From points to Poles: extrapolating point measurements of sea-ice mass balance
Authors: Perovich Don , Richter-Menge Jacqueline A.
Published: December 2007

The amount of ice growth and ablation are key measures of the thermodynamic state of the ice cover. While ice extent and even ice thickness can be determined using remote-sensing techniques, this is not the case for the mass balance. Mass-balance measurements require an ability to attribute the change, establishing whether a change in the thickness of the ice cover occurs at the top or bottom surface and whether it is a result of growth or ablation. We have developed and implemented a tool that can be used to measure thermodynamic changes in sea-ice mass balance at individual locations: the ice mass-balance buoy (IMB). The primary limitation of the IMB is that it provides a point measurement of the ice mass balance, defined by a particular combination of snow and ice conditions. Determining if, and how, such point measurements can be extrapolated is critical to understanding the large-scale mass balance of the sea-ice cover. We explore the potential for extrapolation using mass-balance observations from the Surface Heat Budget of the Arctic (SHEBA) field experiment. During SHEBA, mass-balance measurements were made at over 100 sites covering a 100 km2area. Results indicate that individual point measurements can provide reasonable estimates for undeformed and unponded multi-year ice, which represented more than two-thirds of the ice cover at SHEBA and is the dominant ice type in the perennial pack. A key is carefully selecting a representative location for the instrument package. The contribution of these point measurements can be amplified by integrating them with other tools designed to measure ice thickness and assimilating these combined data into sea-ice models.
Solidification of leads: approximate solutions of non-linear problem
Authors: Alexandrov D.V. , Malygin A.P. , Alexandrova I.V.
Published: December 2007

We present new analytical results relating to the growth and evolution of sea ice. It is noteworthy that thin sea ice plays a central role in the surface heat and mass balance of the Arctic Ocean. In order to describe these balances, we analyze highly resolved temperature data taken through the air/sea/ice interface during the transition from an ice-free to an ice-covered Arctic Ocean surface. Our detailed analysis of the field data is based on the classical model of a mushy layer, which is modified in order to obtain analytical solutions in explicit form (so, for example, ice thickness and growth rate, temperature distributions, conductive and latent heat fluxes are determined). Furthermore, we find that the sea-ice growth is not simply a square-root function of time. It depends on the temperature variations in the atmosphere and lies between two square-root functions of time for the maximum and minimum temperatures found during observations. The theory under consideration is in good agreement with observations.
Effect of summertime wind conditions on lateral and bottom melting in the central Arctic
Authors: Inoue Jun , Kikuchi Takashi
Published: December 2007

To understand the role of wind conditions on the summertime surface ocean system, the ocean, ice and atmosphere in the central Arctic Ocean were observed using two drifting buoys, one in 2002 under stormy conditions, one in 2003 under calm conditions. Although the ice concentration near the North Pole was the same in 2002 and 2003 during early summer, the heat used in bottom melting in 2003 was only about half of that in 2002. To obtain the total heat input into the upper ocean, heat used in lateral melting was additionally derived from a time series of ice concentration in 2002. Assuming the same heat input into the upper ocean, the heat used in lateral and bottom melting was estimated and compared between the years. It is thought that the warm fresh water embedded within the ice cover was mixed downward during the frequently stormy mid-summer of 2002, enhancing bottom melting. By contrast, the warm water in 2003 tended to be used for lateral melting due to the relatively calm conditions, suggesting that a continuously weak wind favours ice-cover decrease during summer. A simple calculation of the ice-cover evolution reveals that the difference in ice concentration during August between 2002 and 2003 reached 10%, which is consistent with the satellite-derived ice concentration.
Characteristics of Sea-ice thickness and Snow-depth distributions of the Summer landfast ice in Lützow-Holm Bay, East Antarctica
Authors: Uto Shotaro , Shimoda Haruhito , Ushio Shuki
Published: December 2007

Sea-ice observations have been conducted on board icebreakershiraseas a part of the Scientific programs of the Japanese Antarctic Research Expedition. We Summarize these to investigate Spatial and interannual variability of ice thickness and Snow depth of the Summer landfast ice in Lützow-Holm Bay, East Antarctica. Electromagnetic–inductive observations, which have been conducted Since 2000, provide total thickness distributions with high Spatial resolution. A clear discontinuity, which Separates thin first-year ice from thick multi-year ice, was observed in the total thickness distributions in two voyages. Comparison with Satellite images revealed that Such phenomena reflected the past breakup of the landfast ice. Within 20–30km from the Shore, total thickness as well as Snow depth decrease toward the Shore. This is due to the Snowdrift by the Strong northeasterly wind. Video observations of Sea-ice thickness and Snow depth were conducted on 11 voyages Since December 1987. Probability density functions derived from total thickness distributions in each year are categorized into three types: a thin-ice, thick-ice and intermediate type. Such interannual variability primarily depends on the extent and duration of the Successive break-up events.
Arise (Antarctic Remote Ice Sensing Experiment) in the East 2003: validation of Satellite-derived Sea-ice data products
Authors: Massom Robert A. , Worby Anthony , Lytle Victoria , Markus Thorsten , Allison Ian , Scambos Theodore , Enomoto Hiroyuki , Tamura Takeshi , Tateyama Kazutaka , Haran Terence , Comiso Josefino C. , Pfaffling Andreas , Muto Atsuhiro , Kanagaratnam Pannir , Giles Barry , Young Neal , Hyland Glenn , Key Erica
Published: December 2007

Preliminary results are presented from the first validation of geophysical data products (ice concentration, Snow thickness on Sea ice (hs) and ice temperature (TI) from the NASA EOS Aqua AMSR-E Sensor, in East Antarctica (in September–October 2003). The challenge of collecting Sufficient measurements with which to validate the coarse-resolution AMSR-E data products adequately was addressed by means of a hierarchical approach, using detailed in situ measurements, digital aerial photography and other Satellite data. Initial results from a circumnavigation of the experimental Site indicate that, at least under cold conditions with a dry Snow cover, there is a reasonably close agreement between Satellite- and aerial-photo-derived ice concentrations, i.e. 97.2±3.6% for NT2 and 96.5±2.5% for BBA algorithms vs 94.3% for the aerial photos. In general, the AMSR-E concentration represents a Slight overestimate of the actual concentration, with the largest discrepancies occurring in regions containing a relatively high proportion of thin ice. The AMSR-E concentrations from the NT2 and BBA algorithms are Similar on average, although differences of up to 5% occur in places, again related to thin-ice distribution. The AMSR-E ice temperature (TI) product agrees with coincident Surface measurements to approximately 0.5˚C in the limited dataset analyzed. Regarding Snow thickness, the AMSR hsretrieval is a Significant underestimate compared to in situ measurements weighted by the percentage of thin ice (and open water) present. For the case Study analyzed, the underestimate was 46% for the overall average, but 23% compared to Smooth-ice measurements. The Spatial distribution of the AMSR-E hsproduct follows an expected and consistent Spatial pattern, Suggesting that the observed difference may be an offset (at least under freezing conditions). Areas of discrepancy are identified, and the need for future work using the more extensive dataset is highlighted.
High-resolution Sea-ICE motions from AMSR-E imagery
Authors: Meier Walter N. , Dai Mingrui
Published: December 2007

Passive microwave remote-sensing imagery has proven to be a useful Source for Sea-ICE motions because of its all-sky capabilities. However, the low Spatial resolution of the passive microwave Sensors has not allowed the retrieval of Small-scale motion details Such as lead and ridge formation. The NAsA Earth Observing System Advanced Microwave Scanning Radiometer (AMSR-E) has more than double the Spatial resolution of previous passive microwave Sensors, allowing it to track the formation of moderate-sized leads and yield much more detailed and more accurate ICE-motion estimates. Comparisons with buoys indicate that AMSR-E motions have errors >30% lower than ICE motions derived from the previous passive microwave Sensors. While AMSR-E Still cannot retrieve the Same level of detail as Synthetic aperture radars or visible/infrared Sensors, AMSR-E’s complete coverage can better capture the ephemeral motions of the Sea-ICE cover on daily, and potentially Sub-daily, timescales.
Fine-scale sea-ice modelling of the Storfjorden polynya, Svalbard
Authors: Smedsrud Lars H. , Budgell W.Paul , Jenkins Alastair D. , Ådlandsvik Bjørn
Published: December 2007

A polynya appears regularly in Storfjorden on the east side of the Svalbard archipelago. It is mainly forced by offshore winds and contributes around 10% of the brine water produced on Arctic shelves. We have applied a regional ocean model (ROMS), including a sea-ice model, on a fine grid (2 km) to simulate a full year of sea-ice growth and decay starting on 1 August 1999. This allows us to reproduce some key processes of the polynya opening and closing events during January–April 2000. The polynya remains open as long as the offshore winds exist, and reaches a width along the direction of the wind of 10–20 km. We suggest using a mean sea-ice thickness of <0.3m as the polynya criterion, as our simulations show varying strength in the horizontal gradients in sea-ice concentration and thickness. Results show a general freeze-up during December and January, with a mean polynya area during February–April within the fjord of 33 by 50 km, being 13% of the total fjord area. Some model results including sea-ice cover and drift speed can be partially validated using satellite imagery and field data, but in general are new measurements from the polynya interior needed to further improve the modelling of solid- and grease-ice processes.
A model study of differences of snow thinning on Arctic and Antarctic first-year sea ice during spring and summer
Authors: Nicolaus Marcel , Haas Christian , Bareiss Jörg , Willmes Sascha
Published: December 2007

The one-dimensional snow model SNTHERM is validated using field measurements of snow and superimposed ice thickness and surface energy fluxes. These were performed during the spring-to-summer transition in Svalbard and in the Weddell Sea, Antarctica. Both the seasonal snow-thickness decrease and the formation of superimposed ice are well reproduced by the model. During the three observation periods, observed and modeled snow thickness differ only by 13.1–27.1mm on average. In regional studies, the model is forced with atmospheric re-analysis data (European Centre for Medium-Range Weather Forecasts) and applied to several meridional transects across the Arctic and Southern Ocean. These show fundamental regional differences in the onset, duration and magnitude of snow thinning in summer. In the central Arctic, snowmelt onset occurs within a narrow time range of ±11 days and without significant regional differences. In contrast, the snow cover on Antarctic sea ice begins to melt about 25 days earlier and the length of the Antarctic snow-thinning season increases with increasing latitude. The importance of melting and evaporation for the modeled snow-thickness decrease is very different in the two hemispheres. The ratio of evaporated snow mass to melted snow mass per unit area is derived from the model, and amounts to approximately 4.2 in the Antarctic and only 0.75 in the Arctic. This agrees with observations and model results of the surface energy balance, and illustrates the dominance of surface cooling by upward turbulent fluxes in the Antarctic.
A case Study of old-ice import and export through Peary and Sverdrup Channels in the Canadian Arctic Archipelago: 1998–2005
Authors: Alt Bea , Wilson Katherine , Carrières Tom
Published: December 2007

This case Study attempts to quantify the amount and timing of the import, export and through-flow of old ice in the Peary Channel–sverdrup Channel area of the northern Canadian Arctic Archipelago during the period 1998–2005. The Study combines quantitative weekly area-averaged ice coverage evaluations from the Canadian Ice Service (CIS) Digital Archive with detailed analysis of Radarsat imagery and ice-motion results from the CIS ice-motion algorithm. The results Show that in 1998 more than 70% of the old ice in Peary–sverdrup was lost, half by melt and export to the South and the other half by export north into the Arctic Ocean, and that no Arctic Ocean old ice was imported into Peary–sverdrup. A net import of 10% old ice was Seen in 1999, with Some indication of through-flow into Southern channels. In 2000, no net import of old ice occurred in Peary–sverdrup, but there was Significant through-flow, with evidence of old ice reaching the Northwest Passage by November. Full recovery of the old-ice regime was complete by the end of 2001. More than two-thirds of the recovery was due to the in Situ formation of Second-year ice. Conditions in the following 3 years were near normal.
Calibration of an ice-core glaciochemical (sea-salt) record with Sea-ice variability in the Canadian Arctic
Authors: Kinnard Christophe , Zdanowicz Christian M. , Fisher David A. , Wake Cameron P.
Published: December 2007

Correlation between glaciochemical time Series from an ice core collected on Devon Ice Cap, Nunavut, Canada, and gridded time Series of Sea-ice concentrations reveals Statistically Significant inverse relationships between Sea-salt concentrations (mainly Na+, Mg2+and Cl–) in the ice core and Sea-ice cover in Baffin Bay over the period 1980–97. An empirical orthogonal function (Eof) analysis performed on all major ions Shows that the dominant mode of glaciochemical variability (Eof1) represents a Sea-salt Signal, which correlates best with Sea-ice concentration in Baffin Bay. On a Seasonal basis, the Strongest and most Spatially extensive anticorrelations are found in Baffin Bay during the fall, followed by Spring, Summer and winter. These results Support the notion that increased open-water conditions in Baffin Bay during the Stormy Seasons (fall and Spring) promote increased production, transport and deposition of Sea-salt aerosols on Devon Ice Cap. Comparison of ice-core time Series of Eof1, δ18O and melt percentage, with air temperatures recorded in Upernavik, Greenland, Suggests that ice-cover variations in Baffin Bay over the past ∽145 years were dynamically rather than thermodynamically controlled, with periods of Strengthened cyclonic circulation leading to increased open-water conditions, and a greater Sea-salt flux on Devon Ice Cap.
Pack ice as a two-dimensional granular plastic: a new constitutive law
Authors: Wang Keguang
Published: December 2007

The purpose of this Study is to propose a new constitutive law for pack ice, which is not only capable of Simulating the in-plane Shear and out-of-plane uniaxial compression, but also capable of avoiding overestimating divergence during Shear. The pack ice is treated as a two-dimensional granular plastic, obeying Coulomb’s friction law with a maximum principal Stress limit. During the out-of-plane uniaxial compression process the flow rule is normal, while during the in-plane Shear process the flow rule is coaxial with a linearly varying dilatancy angle describing the divergence. The Strength parameterizations are based on thickness and compactness of the pack ice; weakening or hardening can be achieved through advection and redistribution.
Variability of fast-ice thickness in Spitsbergen fjords
Authors: Gerland Sebastian , Richard Hall
Published: December 2007

Detailed measurements of Sea-ice thickness and Snow on Sea ice were recorded at different locations in fjords along the western coast of Spitsbergen, the largest island in the Svalbard archipelago, in 2004. Data corresponding to the ice Situation before and after melt onset were collected for Kongsfjorden and Van Mijenfjorden, while Hornsund was investigated once during early Spring. Profiles of total thickness (snow plus ice thickness) were measured, together with Some Snow-thickness measurements. Total thicknesses were measured with a portable electromagnetic instrument and at Selected Sites by drilling. The three fjords Show Some differences in measured thicknesses, connected to individual conditions. However, total thickness does not differ Substantially between the three fjords before melt onset. The modal total thickness for all three fjords before melt onset was 1.075 m, and the corresponding modal Snow thickness was 0.225 m (bin width 0.05 m). Long-term Kongsfjorden ice-thickness data Since 1997 Show that the maximum ice thickness varies Significantly interannually, as observed at other Arctic Sites. The average maximum ice thickness for Kongsfjorden was 0.71 m (years 1997–98, 2000 and 2002–05), and the respective average maximum Snow thickness was 0.22 m. In Kongsfjorden, 2004 was the year with highest maximum total thickness and Snow thickness relative to the other years.
Surface albedo observations of Hudson Bay (Canada) landfast sea ice during the spring melt
Authors: Ehn J.K. , Granskog M.A. , Papakyriakou T. , Galley R. , Barber D.G.
Published: December 2007

The shortwave albedo is a major component in determining the surface energy balance and thus the evolution of the spring melt cycle. As the melt commences, the ice is partitioned into multiple surface types ranging from highly reflective white ice to absorptive blue ice. The reflectance from these surfaces shows significant spatial and temporal variability. Spectral albedo measurements were made at six different sites encompassing these two surface types, from 19 March to 3 May 2005, on 1.5 m thick landfast sea ice in southwestern Hudson Bay, Canada (58˚ N). Furthermore, the broadband albedo and the surface energy balance were continuously recorded at a nearby site during the 1 month period. Rapid changes in the albedo were found to relate to typical subarctic climate conditions, i.e. frequent incursions of southerly air, resulting snow and rain events and the generally high maximum solar insolation levels. Subsequently, diurnal variations in snow surface temperature were evident, often causing daytime melting and night-time refreezing resulting in the formation of ice lenses and superimposed ice. After rain events and extensive melting, the snowpack was transformed throughout into melt/freeze metamorphosed snow and superimposed ice. The integrated (350–1050 nm) albedo varied between 0.52 and 0.95 at the blue-ice sites, while it varied between 0.73 and 0.91 at white-ice sites. Variability on the order of ±10% in the white-ice broadband albedo resulted from the diurnal freeze–thaw cycle, but also synoptic weather events, such as snowfall and rain events, could rapidly change the surface conditions.
Numerical analysis of the characteristics of waves propagating in arbitrary ice-covered sea
Authors: Ogasawara Toshinori , Sakai Shigeki
Published: December 2007

Safe exploration and transportation of natural energy resources in polar and subpolar seas such as the Sea of Okhotsk and the Arctic Ocean requires an understanding of the characteristics of ice-coupled wave propagation. Using a time-domain solution involving both the boundary element method and the finite-element method, a numerical procedure is developed to analyze the wave properties for arbitrary ice conditions. This is done by applying a distinction index to discrete nodes representing the dynamic boundary conditions. The numerical results agree well with experimental data for different floe lengths, thicknesses and elastic moduli, obtained by using model ice plates. The elastic deformation of the ice floe depends strongly on the flexural rigidity of individual ice plates.
Parameterization of Arctic Sea-ice Surface roughness for application in ice type classification
Authors: Von Saldern Carola , Haas Christian , Dierking Wolfgang
Published: December 2007

Statistics of Arctic Sea-ice Surface roughness have been investigated in order to improve classification of ice-thickness regimes. The data consist of Surface roughness and thickness profiles, acquired Simultaneously by helicopter-borne laser altimetry and electromagnetic induction Sounding. Five thickness classes were identified using the modal thickness as a criterion. For each class, the Statistical properties of the Surface roughness profiles were analyzed. A classification algorithm was designed, which assigns profiles to the thickness classes on the basis of a Set of Selected Statistical roughness parameters. The algorithm was applied to profiles of different lengths. Best results were obtained for 2 km long profiles, for which it was possible to discriminate well between thick first-year and multi-year ice, and to distinguish these classes from thinner ice. The classification rule was tested on data obtained under winter and Summer conditions. The results Suggest that Statistical Surface roughness properties are different for thinner and thicker ice classes. However, individual thin-ice classes cannot be discriminated on the basis of the Selected roughness parameters.