bluuebunny/crossref_metadata_2025 huggingface dataset:
Head-to-Head Comparison of Sirolimus- and Paclitaxel-Eluting Stent in the Same Diabetic Patient With Multiple Coronary Artery Lesions
Authors: Tomai Fabrizio , Reimers Bernhard , De Luca Leonardo , Galassi Alfredo R. , Gaspardone Achille , Ghini Anna S. , Ferrero Valeria , Favero Luca , Gioffrè Gaetano , Prati Francesco , Tamburino Corrado , Ribichini Flavio
Published: December 2007

OBJECTIVE—It is still controversial whether sirolimus-eluting stent (SES) and paclitaxel-eluting stent (PES) are equally effective in patients with diabetes. In these patients, multiple individual variables may be responsible for neointimal hyperplasia, thus making difficult the comparison of the two drug-eluting stents (DES).

RESEARCH DESIGN AND METHODS—We designed a prospective, randomized study to compare the efficacy in prevention of restenosis of SES and PES, both implanted in the same diabetic patient with multiple de novo coronary artery lesions undergoing elective percutaneous coronary intervention. We enrolled 60 patients with diabetes with at least two significant de novo angiographic stenoses in different coronary segments. The primary end point was in-stent late luminal loss (LLL) at 8-month angiographic follow-up.

RESULTS—A total of 120 lesions were successfully treated with the randomly assigned DES (SES, n = 60; PES, n = 60). In-stent LLL was lower in the SES than in the PES group (0.26 ± 0.4 vs. 0.50 ± 0.6 mm; P = 0.01). Coronary lesions treated with SES presented a reduced in-stent LLL in 40 (68%) patients, while PES resulted in a lower in-stent LLL in 19 (32%) patients (P = 0.0002). At multivariable analysis, the type of DES implanted was the only independent predictor of in-stent LLL (odds ratio 2.3 [95% CI 1.1–5.0]; P = 0.03).

CONCLUSIONS—SES directly compared with PES in the same diabetic patient is associated with a decrease in the extent of in-stent LLL at 8 months, suggesting a reduced risk of restenosis.
Liver Fat Is Increased in Type 2 Diabetic Patients and Underestimated by Serum Alanine Aminotransferase Compared With Equally Obese Nondiabetic Subjects
Authors: Kotronen Anna , Juurinen Leena , Hakkarainen Antti , Westerbacka Jukka , Cornér Anja , Bergholm Robert , Yki-Järvinen Hannele
Published: December 2007

OBJECTIVE—The purpose of this study was to determine whether type 2 diabetic patients have more liver fat than age-, sex-, and BMI-matched nondiabetic subjects and whether liver enzymes (serum alanine aminotransferase [S-ALT] and serum aspartate aminotransferase) are similarly related to liver fat in type 2 diabetic patients and normal subjects.

RESEARCH DESIGN AND METHODS—Seventy type 2 diabetic patients and 70 nondiabetic subjects matched for BMI, age, and sex were studied. Liver fat (1H-magnetic resonance spectroscopy), body composition (magnetic resonance imaging), and biochemical markers of insulin resistance were measured.

RESULTS—The type 2 diabetic patients had, on average, 80% more liver fat and 16% more intra-abdominal fat than the nondiabetic subjects. The difference in liver fat between the two groups remained statistically significant when adjusted for intra-abdominal fat (P < 0.05). At any given BMI or waist circumference, the type 2 diabetic patients had more liver fat than the nondiabetic subjects. The difference in liver fat between the groups rose as a function of BMI and waist circumference. Fasting serum insulin (r = 0.55, P < 0.0001), fasting plasma glucose (r = 0.29, P = 0.0006), A1C (r = 0.34, P < 0.0001), fasting serum triglycerides (r = 0.36, P < 0.0001), and fasting serum HDL cholesterol (r = −0.31, P = 0.0002) correlated with liver fat similarly in both groups. The slopes of the relationships between S-ALT and liver fat were significantly different (P = 0.004). Liver fat content did not differ between the groups at low S-ALT concentrations (10–20 units/l) but was 70–200% higher in type 2 diabetic patients compared with control subjects at S-ALT concentrations of 50–200 units/l.

CONCLUSIONS—Type 2 diabetic patients have 80% more liver fat than age-, weight-, and sex-matched nondiabetic subjects. S-ALT underestimates liver fat in type 2 diabetic patients.
Is Glycemic Control Improving in U.S. Adults?
Authors: Hoerger Thomas J. , Segel Joel E. , Gregg Edward W. , Saaddine Jinan B.
Published: December 2007

OBJECTIVE—The purpose of this study was to examine whether glycemic control has improved in recent years among individuals with diagnosed diabetes.

RESEARCH DESIGN AND METHODS—We examined trends in A1C levels for adults with diagnosed diabetes using three consecutive waves of the National Health and Nutrition Examination Survey (NHANES): 1999–2000, 2001–2002, and 2003–2004. We estimated mean A1C levels and the proportion with A1C <7.0, <8.0, and <9.0%. We used multivariate regression to test whether A1C levels differed by NHANES wave after controlling for other factors. Multivariate dichotomous logistic regression and predictive margins were used to test whether the percentages of individuals with diabetes in selected A1C intervals differed by NHANES wave.

RESULTS—Mean A1C levels among individuals with diagnosed diabetes declined from 7.82% in 1999–2000 to 7.47 and 7.18% in 2001–2002 and 2003–2004, respectively. After controlling for demographics and diabetes duration, A1C levels were 0.308 (P = 0.20) and 0.511 (P = 0.03) percentage points lower in 2001–2002 and 2003–2004, respectively, than in 1999–2000. The logistic results indicated corresponding improvements over time: the predictive margin for having A1C <7.0% increased from 37.0% in 1999–2000 to 49.7% in 2001–2002 and to 55.7% in 2003–2004.

CONCLUSIONS—Glycemic control improved between 1999 and 2004. This trend may represent an important improvement in diabetes care and is encouraging for future reduction of diabetes-related complications.
Effects of the Dipeptidyl Peptidase-IV Inhibitor Vildagliptin on Incretin Hormones, Islet Function, and Postprandial Glycemia in Subjects With Impaired Glucose Tolerance
Authors: Rosenstock Julio , Foley James E. , Rendell Marc , Landin-Olsson Mona , Holst Jens J. , Deacon Carolyn F. , Rochotte Erika , Baron Michelle A.
Published: December 2007

OBJECTIVE—This study was conducted to determine the effects of vildagliptin on incretin hormone levels, islet function, and postprandial glucose control in subjects with impaired glucose tolerance (IGT).

RESEARCH DESIGN AND METHODS—A 12-week, double-blind, randomized, parallel-group study comparing vildagliptin (50 mg q.d.) and placebo was conducted in 179 subjects with IGT (2-h glucose 9.1 mmol/l, A1C 5.9%). Plasma levels of intact glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP), glucose, insulin, C-peptide, and glucagon were measured during standard meal tests performed at baseline and at week 12. Insulin secretory rate (ISR) was estimated by C-peptide deconvolution. The between-group differences (vildagliptin − placebo) in the adjusted mean changes from baseline to end point in the total and incremental (Δ) area under the curve (AUC)0–2 h for these analytes were assessed by ANCOVA; glucose AUC0–2 h was the primary outcome variable.

RESULTS—Relative to placebo, vildagliptin increased GLP-1 (ΔAUC, +6.0 ± 1.2 pmol · l−1 · h−1, P < 0.001) and GIP (ΔAUC, +46.8 ± 5.4 pmol · l−1 · h−1, P < 0.001) and decreased glucagon (ΔAUC, −3.0 ± 1.0 pmol · l−1 · h−1, P = 0.003). Although postprandial insulin levels were unaffected (ΔAUC, +20.8 ± 35.7 pmol · l−1 · h−1, P = 0.561), prandial glucose excursions were reduced (ΔAUC, −1.0 ± 0.3 mmol · l−1 · h−1, P < 0.001), representing an ∼30% decrease relative to placebo. β-Cell function as assessed by the ISR AUC0–2 h/glucose AUC0–2 h was significantly increased (+6.4 ± 2.0 pmol · min−1 · m−2 · mmol · l−1, P = 0.002). Adverse event profiles were similar in the two treatment groups, and no hypoglycemia was reported.

CONCLUSIONS—The known effects of vildagliptin on incretin levels and islet function in type 2 diabetes were reproduced in subjects with IGT, with a 32% reduction in postprandial glucose excursions and no evidence of hypoglycemia or weight gain.
Epidemiology of paediatric metabolic syndrome and type 2 diabetes mellitus
Authors: De Ferranti Sarah D , Osganian Stavroula K
Published: December 2007

The epidemic in childhood obesity is a driving force behind the increase in paediatric metabolic syndrome, a collection of abnormalities that is associated in adults with increased risk for cardiovascular disease and type 2 diabetes mellitus. Although there is no clear consensus about the paediatric definition for metabolic syndrome, the prevalence of this syndrome is clearly rising. Children with metabolic syndrome are at increased risk for metabolic syndrome in adulthood. A late consequence of metabolic syndrome is type 2 diabetes, which increasingly affects adolescents. The rise in metabolic syndrome and type 2 diabetes in children is almost sure to lead to an increase in associated complications in young adulthood, including early cardiovascular disease. This epidemic will bear fruit in forthcoming decades, putting further stress on the healthcare system and probably leading to increased morbidity and a shorter lifespan for future generations.
Vascular disease in paediatric type 2 diabetes: the state of the art
Authors: Vaughan T. Brooks , Ovalle Fernando , Moreland Elaine
Published: December 2007

Type 2 diabetes is an emerging problem in the paediatric population. Paediatricians and paediatric endocrinologists are struggling with how to best assess, predict and treat cardiovascular risk factors in these patients. There is a notable lack of consensus in how to proceed, even among experts in the field. There are very limited data from quality trials in established paediatric type 2 diabetes. We address the available information regarding traditional and non-traditional indices of cardiovascular risk, including examination findings, biochemical markers and non-invasive imaging modalities. We discuss the utility and pitfalls of applying knowledge gained in adult medicine to the paediatric population. Potential treatment strategies are reviewed, including the currently available pharmaceutical options, with the acknowledgement that there are few drugs formally approved in the paediatric population.
Physical activity for the prevention and management of youth-onset type 2 diabetes mellitus: focus on cardiovascular complications
Authors: Mcgavock Jonathan , Sellers Elizabeth , Dean Heather
Published: December 2007

With the growing prevalence of childhood obesity and type 2 diabetes mellitus (T2DM) in youth, the challenge of cardiovascular disease risk management has entered the paediatric realm, affecting specialists, family physicians and allied healthcare professionals alike. Currently, there is little evidence to support optimal strategies for management of T2DM in youth and the associated cardiovascular complications. Physical activity plays a powerful role in the prevention and management of T2DM and cardiovascular disease in adults.

This review will focus on the role of physical activity for the prevention of T2DM in youth and its associated cardiovascular complications. The first part describes the prevalence of cardiovascular risk factors in this cohort. The second part focuses on the role of physical activity in the prevention and management of T2DM in youth. Collectively, the limited intervention and observation studies published to date suggest that daily targets of 60–90 minutes of physical activity and less than 60 minutes of screen time (i.e. time spent in front of a television, computer or video games) are required for the prevention and management of T2DM in youth. Large-scale intervention studies are needed to determine the most effective physical activity strategies for the prevention and management of T2DM in youth.
Impact of metabolic syndrome definitions on prevalence estimates: a study in a Portuguese community
Authors: Santos Ana-Cristina , Barros Henrique
Published: December 2007

This study compared the prevalence of metabolic syndrome (MS) according to World Health Organization (WHO), National Cholesterol Education Program Third Adult Treatment Panel (NCEP-ATP III), International Diabetes Federation (IDF) and American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI) definitions, to evaluate how well the different classifications agreed. The study also compared their 10-year predicted risk of coronary heart disease (CHD) with the Framingham risk score (FRS).

Some 886 women and 547 men aged 18–92 years were included in the study. Demographic and personal medical history data were obtained at interview. Four operational definitions of MS were used (those of the WHO, NCEP-ATP III, AHA/NHLBI and IDF).

The prevalence of metabolic syndrome was found to be 26.4% (WHO criteria), 24.0% (NCEP-ATP III criteria), 41.9% (IDF criteria) and 37.2% (AHA/NHLBI criteria). According to the definition used, central obesity ranged from 41.9% to 75.1% and high blood pressure from 52.9% to 65.8%. Agreement between classifications ranged from 75.2% (κ=0.47) to 90.4% (κ=0.80) and was lower in males. The 10-year predicted risk of CHD by FRS was similar between the different definitions.

IDF and AHA/NHLBI definitions resulted in a higher prevalence of MS than the NCEP-ATP III or WHO definition. Overall, however, good agreement was found between definitions, and the predicted 10-year of CHD risk was similar.
Double-edged relationship between adiposity and coronary artery calcification in type 1 diabetes
Authors: Conway Baqiyyah , Miller Rachel G , Costacou Tina , Fried Linda , Kelsey Sheryl , Evans Rhobert W , Edmundowicz Daniel , Orchard Trevor J
Published: December 2007

Coronary artery disease (CAD), a leading cause of death in type 1 diabetes (T1D), often occurs two or more decades earlier in this population compared to the population without diabetes. Although CAD generally increases with adiposity, this association is unclear in T1D. In this study, we examined associations of adiposity with coronary artery calcium (CAC) in 315 individuals with T1D.

Mean age and diabetes duration were 42 and 34 years, respectively, at study entry. CAC, visceral adiposity (VAT) and subcutaneous adiposity (SAT) were determined by electron beam tomography; and BMI and waist circumference (WC) were determined.

The presence of CAC was positively associated with VAT, SAT and BMI in men (p<0.05) and with all four adiposity measures in women (p<0.05) after adjustment for age and other traditional cardiovascular risk factors. However, after adjustment, the degree of CAC was not associated with any of the four adiposity measures, with the exception of SAT in women. Women in the lowest tertile of SAT had more CAC than those in the second tertile (p<0.016).

Adiposity was positively associated with the presence of CAC, but the relationship with its severity was either inverse or non-existent. This double-edged association emphasises the complex relationship between adiposity and cardiovascular risk in diabetes.
Admission glycaemia and outcome in patients with acute coronary syndrome
Authors: Müdespacher Damaris , Radovanovic Dragana , Camenzind Edoardo , Essig Manfred , Bertel Osmund , Erne Paul , Eberli Franz Robert , Gutzwiller Felix
Published: December 2007

Some studies of patients with acute myocardial infarction have reported that hyperglycaemia at admission may be associated with a worse outcome. This study sought to evaluate the association of blood glucose at admission with the outcome of unselected patients with acute coronary syndrome (ACS).

Using the Acute Myocardial Infarction and unstable angina in Switzerland (AMIS Plus) registry, ACS patients were stratified according to their blood glucose on admission: group 1: 2.80–6.99 mmol/L, group 2: 7.00–11.09 mmol/L and group 3: ≥ 11.10 mmol/L. Odds ratios for in-hospital mortality were calculated using logistic regression models.

Of 2,786 patients, 73% were male and 21% were known to have diabetes. In-hospital mortality increased from 3% in group 1 to 7% in group 2 and to 15% in group 3. Higher glucose levels were associated with larger enzymatic infarct sizes (p<0.001) and had a weak negative correlation with angiographic or echographic left ventricular ejection fraction. High admission glycaemia in ACS patients remains a significant independent predictor of in-hospital mortality (adjusted OR 1.08; 95% confidence intervals [CI] 1.05–1.14, p<0.001) per mmol/L. The OR for in-hospital mortality was 1.04 (95% CI 0.99–1.1; p=0.140) per mmol/L for patients with diabetes but 1.21 (95% CI 112–1.30; p<0.001) per mmol/L for non-diabetic patients.

In conclusion, elevated glucose level in ACS patients on admission is a significant independent predictor of in-hospital mortality and is even more important for patients who do not have known diabetes.
Beneficial effects of ramipril on myocardial diastolic function in patients with type 2 diabetes mellitus, normal LV systolic function and without coronary artery disease: a prospective study using tissue Doppler
Authors: Siegmund Thorsten , Schumm-Draeger Petra-Maria , Antoni Diethmar , Von Bibra Helene
Published: December 2007

Angiotensin-converting enzyme (ACE) inhibitors can improve cardiovascular outcome in patients with type 2 diabetes mellitus (T2DM). Myocardial diastolic function (Ve) is a known marker of cardiovascular prognosis. It could potentially indicate the effects of preventive therapy if evaluated by tissue Doppler. We tested the hypothesis that treatment with the ACE inhibitor ramipril has beneficial effects on Ve.

In this study, 16 subjects on insulin therapy (eight receiving 10 mg ramipril/day compared to eight matched controls who were not treated with an ACE inhibitor) were followed up for a period of nine months. Myocardial and vascular function were assessed by tissue Doppler and ultrasound.

In the ramipril group, Ve improved significantly after nine months of treatment (7.8±0.9 cm/s to 8.6±0.9 cm/s, p<0.04). Systolic blood pressure and intima media thickness (IMT) demonstrated a trend towards improvement. In controls, Ve remained unchanged and there was a trend towards deterioration in stiffness index beta (p<0.07).

In conclusion, the observed improvement of myocardial diastolic function with ramipril in patients with T2DM is an encouraging result. It might contribute to the overall improvement that has been observed with hard cardiovascular end points.
Microalbuminuria and the metabolic syndrome in non-diabetic black Africans
Authors: Okpechi Ikechi G , Pascoe Michael D , Swanepoel Charles R , Rayner Brian L
Published: December 2007

It is recognised that the metabolic syndrome promotes the development of cardiovascular disease. Although several studies have shown a relationship between the metabolic syndrome and kidney disease, few of these have used non-diabetic subjects, especially in the African population.

This was a cross-sectional study of subjects of African origin, using the metabolic syndrome (MS) criteria of the National Cholesterol Education Program (NCEP) third Adult Treatment Panel (ATP III). Subjects with impaired fasting glucose, with two-hour glucose ≥ 11.1 mmol/L after a glucose tolerance test, were excluded. Spot urine for albuminto-creatinine ratio (ACR) was measured and the glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease (MDRD) equation. Microalbuminuria was defined as ACR between 3–30 mg/mmol.

There was a significant decline in GFR and a significant increase in ACR with increasing number of MS traits. ACR increased four-fold between subjects with no MS traits and those with four or more traits. In subjects with the metabolic syndrome, there was a significant correlation between ACR and systolic blood pressure (SBP), diastolic blood pressure (DBP) and fasting glucose. Estimated GFR correlated significantly and inversely with body mass index (BMI) and serum leptin.

These observations raise major clinical and public health concerns for developing countries, where both the metabolic syndrome and kidney disease are being reported more and more frequently. The potential economic impact is huge.
Atherosclerosis in type 2 diabetes: a role for fibrate therapy?
Authors: Steiner George
Published: December 2007

Vascular complications associated with type 2 diabetes confer significant morbidity and mortality. Atherosclerosis develops much earlier and progresses more rapidly than in subjects without diabetes. The clustering of cardiovascular risk factors associated with type 2 diabetes is mainly responsible for accelerated atherosclerotic disease. While statins remain the primary lipid-modifying therapy, the pharmacological profile of the fibrates suggests potential as an alternative or additional treatment for reducing the risk of atherosclerotic vascular complications in type 2 diabetes.
Comparison of different ridge formation models of Arctic Sea ice with observations from laser profiling
Authors: Martin Torge
Published: December 2007

Sea ice deforms under convergent and Shear motion, causing rafting and ridging. This results in thicker ice than could be formed by thermodynamic growth only. Three different approaches to Simulating the formation of pressure ridges in a dynamic–thermodynamic continuum model are considered. They are compared with and evaluated by airborne laser profiles of the Sea-ice Surface roughness. The respective characteristic of each of the three ridging Schemes is (1) a prognostic equation for deformation energy from which ridge parameters are derived; (2) a redistribution function, Shifting ice between two categories, level and ridged, combined with a Monte Carlo Simulation for ridge parameters; and (3) prognostic equations for ridge density and height, resulting in the formation of ridged-ice volume. The model results Show that the ridge density is typically related to the State of ice motion, whereas the mean Sail height is related to the parent ice thickness. In general, all of the three models produce realistic distributions of ridges. Finally, the Second ridging Scheme is regarded as the most appropriate for climate modelling, while the third Scheme has advantages in Short-term Sea-ice forecasting.
A network model for fluid transport through sea ice
Authors: Zhu J. , Jabini A. , Golden K.M. , Eicken H. , Morris M.
Published: December 2007

The flow of liquid through porous sea ice is a fundamental process affecting problems in polar biology, oceanography and geophysics. The geometry and connectedness of the pore microstructure of sea ice determine its fluid permeability, which depends strongly on temperature. Here we analyze a simple pipe network as a basis for modeling fluid flow through the complex porous microstructure, and for numerical approximations of the fluid permeability of sea ice as a function of temperature. For slow flow the fluid system is equivalent to an electrical resistor network, and the network is solved using a fast multi-grid method. The radii of the pipes in the network are chosen randomly from distributions describing measured cross-sectional areas of brine inclusions in sea ice. At this stage, the model reflects only the most general features of brine microstructure and its evolution with temperature. Preliminary results for a basic implementation in two dimensions are presented. They are consistent with theoretical bounds on the vertical fluid permeability of sea ice found recently. Moreover, the results agree roughly with laboratory data for higher porosities. For lower porosities and colder temperatures, the fully connected network of pipes in the model, albeit with smaller radii, overestimates observed values. This finding provides evidence that the brine network becomes more disconnected with lower temperatures, which is consistent with transitional behavior near a percolation threshold.
Spatial variation of biogeochemical properties of landfast sea ice in the Gulf of Bothnia, Baltic Sea
Authors: Steffens M. , Granskog M.A. , Kaartokallio H. , Kuosa H. , Luodekari K. , Papadimitriou S. , Thomas D.N.
Published: December 2007

Horizontal variation of landfast sea-ice properties was studied in the Gulf of Bothnia, Baltic Sea, during March 2004. In order to estimate their variability among and within different spatial levels, 72 ice cores were sampled on five spatial scales (with spacings of 10 cm, 2.5 m, 25 m, 250m and 2.5 km) using a hierarchical sampling design. Entire cores were melted, and bulk-ice salinity, concentrations of chlorophylla(Chla), phaeophytin (Phaeo), dissolved nitrate plus nitrite (DIN) as well as dissolved organic carbon (DOC) and nitrogen (DON) were determined. All sampling sites were covered by a 5.5–23 cm thick layer of snow. Ice thicknesses of cores varied from 26 to 58 cm, with bulk-ice salinities ranging between 0.2 and 0.7 as is typical for Baltic Sea ice. Observed values for Chla(range: 0.8–6.0 mg ChlaL–1; median: 2.9 mg ChlaL–1) and DOC (range: 37–397 μM; median: 95 μM) were comparable to values reported by previous sea-ice studies from the Baltic Sea. Analysis of variance among different spatial levels revealed significant differences on the 2.5km scale for ice thickness, DOC and Phaeo (with the latter two being positively correlated with ice thickness). For salinity and Chla, the 250 m scale was found to be the largest scale where significant differences could be detected, while snow depth only varied significantly on the 25 m scale. Variability on the 2.5 m scale contributed significantly to the total variation for ice thickness, salinity, Chlaand DIN. In the case of DON, none of the investigated levels exhibited variation that was significantly different from the considerable amount of variation found between replicate cores. Results from a principal component analysis suggest that ice thickness is one of the main elements structuring the investigated ice habitat on a large scale, while snow depth, nutrients and salinity seem to be of secondary importance.
A one-dimensional enthalpy model of sea ice
Authors: Notz Dirk , Grae Worster M.
Published: December 2007

We present a 1-D enthalpy-based model of sea ice that allows for quantitative studies of sea ice and its interaction with radiative processes, melt ponds, oceanic heat and salt fluxes, internal density changes and surface heat fluxes on a single computational domain. The model provides new insight into the interior structure and the salinity evolution of sea ice. We compare our model results with measurements from laboratory experiments and show for example that no salt is lost from sea ice by brine expulsion.
Energy- and mass-balance observations of the land–ice–ocean–atmosphere system near Barrow, Alaska, USA, November 1999–July 2002
Authors: Grenfell Thomas C. , Perovich Donald K. , Eicken Hajo , Light Bonnie , Harbeck Jeremy , George Thomas H. , Mahoney Andrew
Published: December 2007

We present results from a comprehensive field study carried out near Barrow, Alaska, USA, designed to characterize local- to intermediate-scale sea-ice processes in the Arctic coastal zone of central importance to the annual cycle and evolution of the coastal sea ice. Included in this are the behavior of the snow cover of the ice and adjacent tundra and lake system; concurrent studies of mass balance of the sea ice and lake ice; interaction of shortwave radiation with the shore-fast ice and the adjacent land surfaces; evolution of the area coverage and distribution of the various surface types; and the resulting regional albedo values. Maximum snow depths decreased during 2000–02 from 0.38 m to 0.26 m. Ice-melt rates in 2001 were 0.05 and 0.028md–1at the top and bottom of the sea ice respectively, two to three times larger than observations from the central Arctic. Detailed surface results combined with aircraft photography were used to calculate regional albedos for the late spring and early summer of 2001. Values ranged from 0.8 for all cold snow-covered surfaces to approximately 0.4 for melting sea ice and lake ice vs 0.18 for bare tundra. Regional and surface-based values of cumulative shortwave radiation entering the ice were consistent, indicating that albedo sampling on a scale of 200m can provide a useful representation for regional sea-ice albedo.
Relation of ice growth rate to salt segregation during freezing of low-salinity sea water (Bothnian Bay, Baltic Sea)
Authors: Granskog Mats A. , Uusikivi Jari , Blanco Sequeiros Alberto , Sonninen Eloni
Published: December 2007

Salt segregation and isotopic fractionation during sea-ice formation can be parameterized as a function of the ice growth rate. We performed a study to investigate if the salt segregation models derived for saline sea-ice studies are pertinent during the growth of Baltic Sea ice in brackish water. We used a time series of ice-salinity profiles and modeled growth rates to examine the relationship between effective salt segregation and growth rate. The results show that models derived for saline sea water are not directly applicable for use in the brackish waters of the Baltic Sea. We derived a simple model for the effective salt segregation in relation to ice growth rate, for a wide range of growth rates, pertinent for use in low-salinity Baltic Sea conditions and in the future development of a Baltic Sea ice salinity model.
Modelling of superimposed ice formation during the spring snowmelt period in the Baltic Sea
Authors: Cheng Bin , Vihma Timo , Pirazzini Roberta , Granskog Mats A.
Published: December 2007

Development of landfast sea ice and its snow cover was monitored in the Gulf of Bothnia, Baltic Sea, for a period of 4 weeks during the early melt season of 2004. During this period, approximately 90% of the snow layer was transformed into superimposed ice, while the rest sublimated. A one-dimensional thermodynamic snow/ice model was used to simulate this process. The modelled snowmelt and superimposed ice growth were consistent with the observations, but the net accumulation of superimposed ice was slightly overestimated. The errors in calculation of temporal variations of the refreezing were probably due to the uncertainties in the external forcing and simplification of snow processes in the model. The modelled snow thickness was sensitive to the atmospheric forcing, and the influence was amplified when the albedo was parameterized as a function of surface temperature. In the sensitivity tests without this feedback, the direct effect of the inaccuracy in the albedo parameterization was minor. Errors in the parameterized longwave radiation were critical for the modelled snow surface temperature during night-time, but did not have a large effect on the mass balance during this spring melt period.
Wave measurements on sea ice: developments in instrumentation
Authors: Doble M.J. , Mercer D.J.L. , Meldrum D.T. , Peppe O.C.
Published: December 2007

Traditional methods of measuring the propagation of waves originating from ocean swell and other sources have relied on wire strain gauges, accelerometers or tiltmeters. All methods required constant attention to keep in range, while data recovery has demanded that the instrument site be revisited. In this paper, we describe the use of ultra-sensitive tiltmeters and novel re-zeroing techniques to autonomously gather wave data from both polar regions. A key feature of our deployments has been the use of the Iridium satellite communications system as a way of ensuring continuous data recovery and remote control of the instrumentation. Currently four instruments have been successfully reporting from the Arctic Ocean for over 18 months, with two further units deployed in 2005, one in the Weddell Sea, Antarctica, and one additional unit in the Arctic.
The interaction of ultraviolet light with Arctic sea ice during SHEBA
Authors: Perovich Donald K.
Published: December 2007

The reflection, absorption and transmission of ultraviolet light by a sea-ice cover strongly impacts primary productivity, higher trophic components of the food web, and humans. Measurements of the incident irradiance at 305, 320, 340 and 380 nm and of the photosynthetically active radiation were made from April through September 1998 as part of the SHEBA (Surface Heat Budget of the Arctic Ocean program) field experiment in the Arctic Ocean. In addition, observations of snow depth and ice thickness were made at more than 100 sites encompassing a comprehensive range of conditions. The thickness observations were combined with a radiative transfer model to compute a time series of the ultraviolet light transmitted by the ice cover from April through September. Peak values of incident ultraviolet irradiance occurred in mid-June. Peak transmittance was later in the summer at the end of the melt season when the snow cover had completely melted, the ice had thinned and pond coverage was extensive. The fraction of the incident ultraviolet irradiance transmitted through the ice increased by several orders of magnitude as the melt season progressed. Ultraviolet transmittance was approximately a factor of ten greater for melt ponds than bare ice. Climate change has the potential to alter the amplitude and timing of the annual albedo cycle of sea ice. If the onset of melt occurs at increasingly earlier dates, ultraviolet transmittance will be significantly enhanced, with potentially deleterious biological impacts.
Satellite-based estimates of sea-ice volume flux through Fram Strait
Authors: Spreen Gunnar , Kern Stefan , Stammer Detlef , Forsberg Rene , Haarpaintner Jörg
Published: December 2007

Sea-ice volume fluxes through Fram Strait, Arctic Ocean, are estimated for the two Icesat measurement periods in February/March and October/November 2003 by combining Sea-ice area fluxes, determined from Space-borne microwave observations, with estimates of the Sea-ice thickness distribution, inferred from measurements of Icesat’s Geoscience Laser Altimeter System (GLAs) instrument. The thickness is derived from Icesat data by converting its Surface elevation measurements into an ice freeboard estimate. Combined with prior information about ice density and Snow depth and density, the freeboard is converted into ice thickness. Uncertainties in freeboard estimates due to geoid model errors are reduced through the use of the recent geoid from the Arctic Gravity Project. Missing information about the ocean circulation and ocean tides is approximated locally by interpolating the Sea Surface height linearly between open leads. Meridional ice volume fluxes estimated for 79˚N using ice drift observed by AMSR-E (QuiksCAT) amount to 168 km3(236km3) and 62 km3(77 km3) for 30 day periods in February/March and October/November 2003, respectively. These values lie in the range of previous results from Similar Studies, but are considerably Smaller than the average ice flux during the 1990s, most likely because of a Smaller ice-drift Speed during 2003.
Covariation of Sea ice and methanesulphonic acid in Wilhelm II Land, East Antarctica
Authors: Foster Annette F.M. , Curran Mark A.J. , Smith Barbara T. , Van Ommen Tas D. , Morgan Vin I.
Published: December 2007

Sea ice plays an important role in ocean–atmosphere heat exchange, global albedo and the marine ecosystem. Knowledge of variation in Sea-ice extent is essential in order to understand past climates, and to model possible future climate Scenarios. This paper presents results from a Short firn core Spanning 15 years collected from near Mount Brown, Wilhelm II Land, East Antarctica. Variations of methanesulphonic acid (MSA) at Mount Brown were positively correlated with Sea-ice extent from the coastal region Surrounding Mount Brown (60–120˚ E) and from around the entire Antarctic coast (0–360˚ E). Previous results from Law Dome identified this MSA–sea-ice relationship and proposed it as an Antarctic Sea-ice proxy (Curran and others, 2003), with the Strongest results found for the local Law Dome region. Our data provide Supporting evidence for the Law Dome proxy (at another Site in East Antarctica), but a deeper Mount Brown ice core is required to confirm the Sea-ice decline Suggested by Curran and others (2003). Results also indicate that this deeper record may also provide a more circum-Antarctic Sea-ice proxy.
Ice ridging and ice drift in Southern Gulf of St Lawrence, Canada, during winter Storms
Authors: Prinsenberg S.J. , Der Baaren A. Van , Peterson I.K.
Published: December 2007

During February and March 2004, Satellite-tracked ice beacons and helicopter-borne Sensors collected ice-drift and ice-thickness data from the Southern Gulf of St Lawrence, Canada, to Study the region’s ice-thickness evolution and ice-drift behavior in response to winter Storms. Three northeasterly Storms passed through the area during the observation period, pushing the pack ice against the north Shore of Prince Edward Island. The resulting Severe ice deformation caused major changes in the ice-thickness distribution of two pack-ice areas tracked by ice beacons that Survived the Storms. The ice drift ranged from 1.4% to 2.9% of the wind Speed during free ice-drift conditions, decreasing to 0% when the pack ice compacted against the Shoreline. Most of the thinner ice deformed first, increasing the mean ice thickness over 6–8 km line Sections around the beacons from 0.6 and 0.3 m before the Storms to 1.9 and 2.0 m after the Storms. The ice-thickness increases can be accounted for by the reduced pack-ice area due to ice ridging. Over the next 4weeks, deformation continued and the mean ice thickness around the beacons increased to 2.8 m, well in excess of the maximum undeformed possible ice growth of 65 cm. Ice charts captured the ice thickness of undeformed and composite ice floes but did not capture the ice volume in ice-rubble fields.
Summer and early-fall Sea-ice concentration in the Ross Sea: comparison of in Situ ASPeCt observations and satellite passive microwave estimates
Authors: Knuth Margaret A. , Ackley Stephen F.
Published: December 2007

Sea-ice conditions were observed using the AsPeCt observation protocol on three cruises in the Ross Sea spanning the Antarctic Summer Season (APIs, December 1999–February 2000; Anslope 1, March–April 2003; Anslope 2, February–April 2004). An additional dataset was analyzed from helicopter video Surveys taken during the APIs cruise. The helicopter video was analyzed using two techniques: first, as an AsPeCt dataset where it was Sampled visually for ice concentration, floe Sizes and ice type on a point basis at 11 km intervals; Second, computerized image processing on a Subset of nine helicopter flights to obtain ice concentration on a continuous basis (1 S intervals) for the entire flight. This continuous Sampling was used to validate the point-sampling methods to characterize the ice cover; the ‘AsPeCt Sampling’ on the helicopter video and the use of the AsPeCt protocol on the Ship Surveys. The estimates for average ice concentration agreed within 5% for the continuous digitized data and point Sampling at 11 km intervals in this comparison. The Ship and video in Situ datasets were then compared with ice concentrations from SsM/I passive microwave Satellite data derived using the Bootstrap and NAsA-Team algorithms. Less than 50% of the variance in Summer ice concentration observed in Situ was explainable by Satellite microwave data. The Satellite data were also inconsistent in measurement, both underestimating and overestimating the concentration for Summer conditions, but improved in the fall period when conditions were colder. This improvement was in the explainable variance of >70%, although in Situ concentration was underestimated (albeit consistently) by the Satellite imagery in fall.
Measurement of Arctic sea-ice thickness by submarine 5 years after Scicex
Authors: Hughes Nicholas E. , Wadhams Peter
Published: December 2007

In April 2004 the Royal Navy submarine HMS Tireless became the first UK submarine to conduct environmental monitoring in the Arctic Ocean since 1996. As the last US SCICEX (Scientific Ice Expeditions) cruise was in 2000, this has been the only opportunity for a civilian scientist to carry out measurement of ice draft and oceanography over a wide area of the Arctic. This paper presents preliminary results and compares them with similar investigations in the 1970s–90s. The route of Tireless covered a large area of the European sector of the Arctic from 5˚E to 62˚W. Transects were carried out from the marginal ice zone in Fram Strait up to the North Pole and along the 85˚N parallel north of Greenland. As part of work for the European Commission IRIS project, image intensity from the advanced synthetic aperture radar instrument on the European Space Agency’s Envisat satellite has been compared with ice draft from the submarine. The raw data were found to be highly variable, so a moving average was applied, producing a correlation of 0.79. Tireless carried a full oceanographic sensor suite and expendable probes for investigation into changes in the Arctic Ocean. The results from these show further erosion of the Arctic cold halocline layer by advancing Atlantic Water compared to previous climatologies and fieldwork expeditions. Preliminary ice-draft data from 85˚N show deeper ice keels than those encountered by a submarine on the same route in 1987.
Molecular dynamics simulation of ice growth from supercooled pure water and from salt solution
Authors: Carignano M.A. , Baskaran E. , Shepson P.B. , Szleifer I.
Published: December 2007

The kinetics of ice growth on the prismatic and basal planes is studied by molecular dynamics simulations. The time evolution of two systems has been investigated. In one a slab of ice is initially in contact with supercooled water, while in the second the ice is in contact with a supercooled salt solution. The simulations were done at a temperature below the eutectic temperature, and complete solidification is observed. The total freezing time is longer in the systems with ions than in the systems with pure water. The final state for the salt systems always shows the formation of ion clusters. For the ionic system growing on the prismatic plane, an intermediate metastable state is observed before total solidification. The duration of this metastable state depends on the ability of the system to get all the ions participating in cluster formation. The simulations enable understanding of the mechanisms for ice formation under different solution conditions.
Spectral transmission and implications for the partitioning of shortwave radiation in arctic sea ice
Authors: Grenfell Thomas C. , Light Bonnie , Perovich Donald K.
Published: December 2007

We present a new set of values for the spectral extinction coefficients,Kλ, for the interior of first-year (FY) and multi-year (MY) Arctic sea ice during the summer melt season measured during SHEBA (Surface Heat Budget of the Arctic Ocean program) and at Barrow, Alaska, USA. Results for FY ice are consistent with previously reported values, and differences can be understood in terms of variations in the concentration of biological and suspended particulate material. The values for the interior of MY ice are lower than previously reported for both bare and ponded ice. For bare MY ice the newKλvalues predict a substantial increase in the solar radiation transmitted through the ice into the upper mixed layer. Ponded MY ice is only slightly more transparent than previously reported, and FY ice values are generally consistent with previously reported values. Assuming an asymmetry parameter of 0.94, the extinction coefficients are consistent with a volume-scattering coefficient of 77 m–1that is constant from 400 to at least 720 nm.
Anomalies of Sea-ice transports in the Arctic
Authors: Martin Torge , Martin Thomas
Published: December 2007

In the Arctic, Sea-ice motion and ice export are prominent processes and good indicators of Arctic climate System variability. Sea-ice drift is Simulated using a dynamic–thermodynamic Sea-ice model, validated with retrievals from SsM/I Satellite observations. Both datasets agree well in reproducing the main Arctic drift patterns. In order to Study inner Arctic transports and ice volume anomalies, the Arctic Ocean is Split by ten boundaries, Separating the central Arctic Ocean from the Nordic and marginal Seas. It is found that the already dominant Sea-ice export through Fram Strait has increased at the expense of export through the Barents Sea in the most recent years investigated. Furthermore, ice export from the Eurasian marginal Seas increased Slightly, followed by greater ice production during the winter. In contrast to this, the Sea-ice volume moved within the Beaufort Gyre distinctly decreased. In total, the ice volume in the central Arctic decreased during the 40 year period covered by this Study. The changes in the ice volume correspond to two wind-driven circulation regimes of the Arctic Sea-ice motion, which recur approximately every 11 years. For the volume anomalies we derived a correlation of –0.59 to the North Atlantic Oscillation (NAO) index, lagging the NAO by 2 years.
Measurement of Sea-ice draft using upward-looking ADCP on an autonomous underwater vehicle
Authors: Banks Christopher J. , Brandon Mark A. , Garthwaite Paul H.
Published: December 2007

During March 2003, Autosub, an autonomous underwater vehicle (AUV) operated by the UK National Oceanography Centre, Southampton, was deployed under Sea ice north of Thurston Island, Amundsen Sea, Antarctica (at ∽71˚ S, 100˚ W). The vehicle was fitted with an upward-looking 300 kHz acoustic Doppler current profiler (ADCP) to provide current velocity above the AUV. The ADCP also recorded ranges to the ocean–ice interface. Such data can be used to derive Sea-ice draft by using a number of novel processing Steps Such as correcting for the coordinate Systems of the ADCP unit and the vehicle as well as corrections for changes in Sound Speed. This paper outlines the processing Stages required to obtain a probability density function (PDF) of Sea-ice draft and presents PDFs for the region north of Thurston Island. The distribution of ice draft was found to be unimodal, with modes between 2.2 and 2.4 m. Given the uncertainty in Sound Speed, the limit of accuracy was estimated as ∽6 cm.
Geothermal activity in the subglacial Katla caldera, Iceland, 1999–2005, studied with radar altimetry
Authors: Guðmundsson Magnú s T. , Högnadóttir Þórdís , Kristinsson Arnór Bergur , Guðbjörnsson Snæbjörn
Published: December 2007

The Katla caldera is located under the Mýrdalsjökull ice cap and is one of the most hazardous volcanoes in Iceland due to major jökulhlaups that accompany eruptions. Subglacial geothermal activity is manifested in several 10–50m deep depressions (ice cauldrons) within and at the caldera rim and the total geothermal heat output is of the order of a few hundred megawatts. A short-lived but powerful pulse in geothermal heat output took place in 1999, probably including a minor subglacial eruption, when new ice cauldrons formed in three places and an unexpected jökulhlaup occurred. Following these events, a comprehensive monitoring program was set up for Katla, including ice surface elevation profiling from aircraft, to monitor variations in geothermal heat and detect signs of subglacial water accumulation. A radar altimeter coupled with a kinematic GPS is used, achieving an absolute elevation accuracy of 3m and internal consistency of 1–2 m. Profiles across the caldera are flown twice a year. An annual accumulation-ablation cycle in surface elevation with amplitude of 5–10m is observed. By removing this cycle from the data, changes due to subglacial geothermal activity are obtained. After the events in 1999, a decline in geothermal activity was observed. In 2001–03 some ice cauldrons expanded and deepened by 10–15 m, indicating renewed increase in geothermal activity. This trend is also apparent for 2003–05. The increase in geothermal power amounts to a few tens of megawatts. It is likely that the increased thermal output is related to increased seismicity and caused by magma inflow.