Impact of debris cover on glacier ablation and atmosphere - glacier feedbacks in the Karakoram

This work was partly carried out under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA) with financial support from the UK Government’s Department for International Development and the International Development Research Centre, Ottawa, Canada.The Karakoram range of the Hindu-Kush Himalaya is characterized by both extensive glaciation and a widespread prevalence of surficial debris cover on the glaciers. Surface debris exerts a strong control on glacier surface-energy and mass fluxes and, by modifying surface boundary conditions, has the potential to alter atmosphere– glacier feedbacks. To date, the influence of debris on Karakoram glaciers has only been directly assessed by a small number of glaciological measurements over short periods. Here, we include supraglacial debris in a high-resolution, interactively coupled atmosphere–glacier modeling system. To investigate glaciological and meteorological changes that arise due to the presence of debris, we perform two simulations using the coupled model from 1 May to 1 October 2004: one that treats all glacier surfaces as debris-free and one that introduces a simplified specification for the debris thickness. The basin-averaged impact of debris is a reduction in ablation of 14 %, although the difference exceeds 5mw:e: on the lowest-altitude glacier tongues. The relatively modest reduction in basin-mean mass loss results in part from non-negligible sub-debris melt rates under thicker covers and from compensating increases in melt under thinner debris, and may help to explain the lack of distinct differences in recent elevation changes between clean and debriscovered ice. The presence of debris also strongly alters the surface boundary condition and thus heat exchanges with the atmosphere; near-surface meteorological fields at lower elevations and their vertical gradients; and the atmospheric boundary layer development. These findings are relevant for glacio-hydrological studies on debris-covered glaciers and contribute towards an improved understanding of glacier behavior in the Karakoram

Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards

In areas of high relief, many glaciers have extensive covers of supraglacial debris in their ablation zones, which alters both rates and spatial patterns of melting, with important consequences for glacier response to climate change. Wastage of debris-covered glaciers can be associated with the formation of large moraine-dammed lakes, posing risk of glacier lake outburst floods (GLOFs). In this paper, we use observations of glaciers in the Mount Everest region to present an integrated view of debris-covered glacier response to climate change, which helps provide a long-term perspective on evolving GLOF risks. In recent decades, debris-covered glaciers in the Everest region have been losing mass at a mean rate of ~ 0.32 m yr⁻¹, although in most cases there has been little or no change in terminus position. Mass loss occurs by 4 main processes: (1) melting of clean ice close to glacier ELAs; (2) melting beneath surface debris; (3) melting of ice cliffs and calving around the margins of supraglacial ponds; and (4) calving into deep proglacial lakes. Modelling of processes (1) and (2) shows that Everest-region glaciers typically have an inverted ablation gradient in their lower reaches, due to the effects of a down-glacier increase in debris thickness. Mass loss is therefore focused in the mid parts of glacier ablation zones, causing localised surface lowering and a reduction in downglacier surface gradient, which in turn reduce driving stress and glacier velocity, so the lower ablation zones of many glaciers are now stagnant. Model results also indicate that increased summer temperatures have raised the altitude of the rain–snow transition during the summer monsoon period, reducing snow accumulation and ice flux to lower elevations. As downwasting proceeds, formerly efficient supraglacial and englacial drainage networks are broken up, and supraglacial lakes form in hollows on the glacier surface. Ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub-debris melt rates, so extensive lake formation accelerates overall rates of ice loss. Most supraglacial lakes are ‘perched’ above hydrological base level, and are susceptible to drainage if they become connected to the englacial drainage system. Speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre-existing weaknesses in the ice. Roof collapses can open these voids up to the surface, and commonly provide the nuclei of new lakes. Thus, by influencing both lake drainage and formation, englacial conduits exert a strong control on surface ablation rates. An important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier. Base-level lakes formed behind intact moraine dams can grow monotonically, and in some cases can pose serious GLOF hazards. Glacier termini can evolve in different ways in response to the same climatic forcing, so that potentially hazardous lakes will form in some situations but not others. Additionally, the probability of a flood is not simply a function of lake volume, but depends on the geometry and structure of the dam, and possible trigger mechanisms such as ice- or rockfalls into the lake. Satellite-based measurements of glacier surface gradient and ice velocities allow probable future locations of base-level lakes to be identified. A base-level lake has begun to grow rapidly on Ngozumpa Glacier west of Mount Everest, and could attain a volume of ~10⁸ m³ within the next 2 or 3 decades. Unless mitigation efforts are undertaken, this lake could pose considerable GLOF hazard potential

Effectiveness of non-pharmacological interventions for fatigue in adults with multiple sclerosis, rheumatoid arthritis, or systemic lupus erythematosus: a systematic review

Aim. This paper reports a systematic review of non-pharmacological interventions for fatigue in adults with three common autoimmune conditions. Background. A considerable proportion of people with multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus experience compromised quality of life due to fatigue. Recent reviews of pharmacotherapies for fatigue in these conditions remain inconclusive, and systematic evidence for effectiveness of non-pharmacological interventions was unavailable. Our paper addresses this gap. Methods. The literature search used the key words fatigue, energy, multiple sclerosis, rheumatoid arthritis and systemic lupus. It included 19 electronic databases and libraries, three evidence-based journals, two internet search engines, was dated 1987–2006, and limited to English. Non-pharmacological experimental studies about fatigue comprising more than five adults were included. Meta-analysis was not possible due to diverse interventions and outcome measures, therefore studies were analysed by types of interventions used to reduce fatigue. Results. Of 653 hits, 162 papers were reviewed, and 36 met the inclusion criteria. Thirty-three primary studies reported 14 randomized controlled trials and 19 quasi-experimental designs. Most interventions were tested with people with multiple sclerosis. Exercise, behavioural, nutritional and physiological interventions were associated with statistically significant reductions in fatigue. Aerobic exercise was effective, appropriate and feasible for reducing fatigue among adults with chronic autoimmune conditions. Electromagnetic field devices showed promise. The diversity of interventions, designs, and using 24 different instruments to measure fatigue, limited comparisons. Conclusion. Low impact aerobic exercise gradually increasing in intensity, duration and frequency may be an effective strategy in reducing fatigue in some adults with chronic auto-immune conditions. However, fatigue is a variable and personal experience and a range of behavioural interventions may be required. Well-designed studies testing these promising strategies and consensus on outcome fatigue measures are needed

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