Interannual Dynamics of Ice Cliff Populations on Debris-Covered Glaciers From Remote Sensing Observations and Stochastic Modeling.

Ice cliffs are common on debris-covered glaciers and have relatively high melt rates due to their direct exposure to incoming radiation. Previous studies have shown that their number and relative area can change considerably from year to year, but this variability has not been explored, in part because available cliff observations are irregular. Here, we systematically mapped and tracked ice cliffs across four debris-covered glaciers in High Mountain Asia for every late ablation season from 2009 to 2019 using high-resolution multi-spectral satellite imagery. We then quantified the processes occurring at the feature scale to train a stochastic birth-death model to represent the cliff population dynamics. Our results show that while the cliff relative area can change by up to 20% from year to year, the natural long-term variability is constrained, thus defining a glacier-specific cliff carrying capacity. In a subsequent step, the inclusion of external drivers related to climate, glacier dynamics, and hydrology highlights the influence of these variables on the cliff population dynamics, which is usually not a direct one due to the complexity and interdependence of the processes taking place at the glacier surface. In some extreme cases (here, a glacier surge), these external drivers may lead to a reorganization of the cliffs at the glacier surface and a change in the natural variability. These results have implications for the melt of debris-covered glaciers, in addition to showing the high rate of changes at their surface and highlighting some of the links between cliff population and glacier state.

Importance and vulnerability of the world's water towers.

Mountains are the water towers of the world, supplying a substantial part of both natural and anthropogenic water demands1,2. They are highly sensitive and prone to climate change3,4, yet their importance and vulnerability have not been quantified at the global scale. Here we present a global water tower index (WTI), which ranks all water towers in terms of their water-supplying role and the downstream dependence of ecosystems and society. For each water tower, we assess its vulnerability related to water stress, governance, hydropolitical tension and future climatic and socio-economic changes. We conclude that the most important (highest WTI) water towers are also among the most vulnerable, and that climatic and socio-economic changes will affect them profoundly. This could negatively impact 1.9 billion people living in (0.3 billion) or directly downstream of (1.6 billion) mountainous areas. Immediate action is required to safeguard the future of the world's most important and vulnerable water towers.

Modifiable and non-modifiable risk factors affecting walking recovery after hip fracture.

UNLABELLED: Modifiable and non-modifiable predictors of mobility recovery were analyzed on a sample of 774 hip fracture patients according to pre-fracture abilities. Overall predictors were mostly non-modifiable factors related to frailty of patients with the exception of 25-hydroxyvitamin D concentration which significantly affected walking recovery, especially in patients with higher pre-fracture performance. INTRODUCTION: This study aims to investigate mobility changes after hip fracture with the aim of identifying modifiable and non-modifiable predictors of mobility recovery according to different pre-fracture abilities. METHODS: This is a prospective inception cohort study of consecutive older patients, admitted with a fragility hip fracture in three Hospitals of Emilia Romagna (Italy). A sample of 774 patients alive at the sixth month was divided into three groups according to pre-fracture ambulation ability (group 1: mobile outdoors; group 2: mobile indoors; and group 3: mobile with help). The relationship between baseline characteristics of patients and the odds of walking recovery was analyzed using multivariate regression analysis. RESULTS: Mortality differed significantly among the three groups and was the highest in patients needing help to walk. Among the survivors, only 50.3 % of patients recovered walking ability. In a multivariate analysis, independent risk factors were different among the three groups. In group 1, older age, comorbidities, the use of walking devices before fracture, and low albumin level acted as negative factors while male gender, a pre-fracture high functional status, and higher 25-hydroxyvitamin D levels increased the probability of full recovery. In group 2, only pre-fracture functional status and 25-hydroxyvitamin D concentration were related to the recovery of walking ability. Pre-fracture functional status was also the only significant predictor for patients in group 3. CONCLUSIONS: Several baseline characteristics of patients are related to the likelihood of recovering walking ability after hip fracture. The 25-hydroxyvitamin D level seems to be the only relevant modifiable factor even if the effectiveness of its supplementation has yet to be demonstrated.

An enhanced temperature index model for debris-covered glaciers accounting for thickness effect.

Debris-covered glaciers are increasingly studied because it is assumed that debris cover extent and thickness could increase in a warming climate, with more regular rockfalls from the surrounding slopes and more englacial melt-out material. Debris energy-balance models have been developed to account for the melt rate enhancement/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya, and can be difficult to extrapolate. Due to their lower data requirements, empirical models have been used extensively in clean glacier melt modelling. For debris-covered glaciers, however, they generally simplify the debris effect by using a single melt-reduction factor which does not account for the influence of varying debris thickness on melt and prescribe a constant reduction for the entire melt across a glacier. In this paper, we present a new temperature-index model that accounts for debris thickness in the computation of melt rates at the debris-ice interface. The model empirical parameters are optimized at the point scale for varying debris thicknesses against melt rates simulated by a physically-based debris energy balance model. The latter is validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. We develop the model on Miage Glacier, Italy, and then test its transferability on Haut Glacier d'Arolla, Switzerland. The performance of the new debris temperature-index (DETI) model in simulating the glacier melt rate at the point scale is comparable to the one of the physically based approach, and the definition of model parameters as a function of debris thickness allows the simulation of the nonlinear relationship of melt rate to debris thickness, summarised by the Østrem curve. Its large number of parameters might be a limitation, but we show that the model is transferable in time and space to a second glacier with little loss of performance. We thus suggest that the new DETI model can be included in continuous mass balance models of debris-covered glaciers, because of its limited data requirements. As such, we expect its application to lead to an improvement in simulations of the debris-covered glacier response to climate in comparison with models that simply recalibrate empirical parameters to prescribe a constant across glacier reduction in melt.

Changes in glaciers in the Swiss Alps and impact on basin hydrology: current state of the art and future research.

Switzerland is one of the countries with some of the longest and best glaciological data sets. Its glaciers and their changes in response to climate have been extensively investigated, and the number and quality of related studies are notable. However, a comprehensive review of glacier changes and their impact on the hydrology of glacierised catchments for Switzerland is missing and we use the opportunity provided by the EU-FP7 ACQWA project to review the current state of knowledge about past changes and future projections. We examine the type of models that have been applied to infer glacier evolution and identify knowledge gaps that should be addressed in future research in addition to those indicated in previous publications. Common characteristics in long-term series of projected future glacier runoff are an initial peak followed by a decline, associated with shifts in seasonality, earlier melt onset and reduced summer runoff. However, the quantitative predictions are difficult to compare, as studies differ in terms of model structure, calibration strategies, input data, temporal and spatial resolution as well as future scenarios used for impact studies. We identify two sources of uncertainties among those emerging from recent research, and use simulations over four glaciers to: i) quantify the importance of the correct extrapolation of air temperature, and ii) point at the key role played by debris cover in modulating glacier response.

Changes of glaciers in the Andes of Chile and priorities for future work.

Glaciers in the Andes of Chile seem to be shrinking and possibly loosing mass, but the number and types of studies conducted, constrained mainly by data availability, are not sufficient to provide a synopsis of glacier changes for the past or future or explain in an explicit way causes of the observed changes. In this paper, we provide a systematic review of changes in glaciers for the entire country, followed by a discussion of the studies that have provided evidence of such changes. We identify a missing type of work in distributed, physically-oriented modelling studies that are needed to bridge the gap between the numerous remote sensing studies and the specific, point scale works focused on process understanding. We use an advanced mass balance model applied to one of the best monitored glaciers in the region to investigate four main research issues that should be addressed in modelling studies for a sound assessment of glacier changes: 1) the use of physically-based models of glacier ablation (energy balance models) versus more empirical models (enhanced temperature index approaches); 2) the importance of the correct extrapolation of air temperature forcing on glaciers and in high elevation areas and the large uncertainty in model outputs associated with it; 3) the role played by snow gravitational redistribution; and 4) the uncertainty associated with future climate scenarios. We quantify differences in model outputs associated with each of these choices, and conclude with suggestions for future work directions.

Vitamin D supplementation is required to normalize serum level of 25OH-vitamin D in older adults: an observational study of 974 hip fracture inpatients.

BACKGROUND: Vitamin D deficiency is highly prevalent in older adults in all continents. In this study we assessed the vitamin D status of hip fracture subjects across different hospitals in a real word situation using the data from a multicenter cohort study on outcomes in orthogeriatric units. METHODS: We performed a prospective cohort study on 974 consecutive patients 75 yr or older admitted with fragility hip fracture over a 12 months period at 4 general hospitals of different districts in Emilia Romagna Region, Italy. Data collected included comorbidity, cognitive impairment, prefracture functional status, walking ability, living arrangement along with the use of antiosteoporotic drugs, serum intact PTH and serum 25-hydroxyvitamin D [25(OH)D]. RESULTS: Mean 25(OH)D serum levels were 12.2±9.4 ng/ml and 84.2% of patients had levels below recommended values. Male had a higher probability to have values within the reference range [odds ratio (OR): 1.74 (1.13-2.67); p=0.012] while living in nursing resulted negatively related even if only close to statistical significance [OR: 0.24 (0.06-1.02); p=0.051]. Vitamin D supplementation appeared to be the strongest factor associated with adequate level of vitamin D levels [OR: 4.50 (2.57-7.88); p<0.001). CONCLUSION: This study confirmed the very high rate of severe vitamin D deficiency in Italian subjects admitted with hip fracture. Our study also showed that supplementation of vitamin D is the strongest determinant influencing serum 25(OH)D level of older persons with hip fracture and these results should be taken into account when planning treatment in older persons.

Comprehensive care.

Comprehensive care (CC) represents the basic approach of orthogeriatric comanaged care with the overall objectives of improving results regarding physical and psychological functions and reducing hospitalization, long-term care placement and mortality. It is a two-stage process that includes the Comprehensive Geriatric Assessment (CGA) and the development and implementation of an interdisciplinary treatment plan based on priority interventions and unmet needs. In older hip fracture patients CC has to face crucial issues such as treatment choice and surgical options, clinical stabilization of patients before surgery and the prevention and treatment of complication in the postoperative phase. The main aim are to avoid inappropriate surgical delays and reduce the overall number of days of immobility endorsing an early ambulation with full weight bearing as tolerated. Multiprofessional CC must also ensure uninterrupted care for transition between the different care levels that patients need after fracture before returning home. Therefore another important issue is a structured discharge plan tailored to the individual patient identifying subjects that could benefit from a skilled or more intensive rehabilitation, identifying patients and family that will probably need a higher level of care even after rehabilitation, determining timing of discharge, defining the continuing care that needs to be provided and finally ensuring the patient has access to available services and resources. However, the implementation of a comprehensive and multidisciplinary co-care model in an orthopedic unit is a difficult task because it is necessary a great effort to change cultural attitudes related to traditional model of care.