University of Aberdeen

About: University of Aberdeen is a education organization based out in Aberdeen, United Kingdom. It is known for research contribution in the topics: Population & Randomized controlled trial. The organization has 21174 authors who have published 49962 publications receiving 2105479 citations. The organization is also known as: Aberdeen University.

Experimental and quasi-experimental designs for evaluating guideline implementation strategies.

Abstract: The choice of study design for guideline implementation studies will determine the confidence with which the observed effects can be attributed to the interventions under study. In general, cluster randomized trials, of which there are different types, provide the most robust design. However, the use of these designs has implications for the power, conduct and analysis of studies. Wherever possible, designs allowing head-to-head comparisons, which incorporate baseline measures of performance, should be used.

Seasonal evolution of subglacial drainage and acceleration in a Greenland outlet glacier

Abstract: An acceleration of ice-mass loss has been observed near the margin of the Greenland ice sheet, partly as a result of faster ice motion. Observations by GPS receivers reveal high seasonal variability in ice motion, with summer motion up to 220% higher than winter background levels. The Greenland ice sheet contains enough water to raise sea levels by 7 m. However, its present mass balance and future contribution to sea level rise is poorly understood1. Accelerated mass loss has been observed near the ice sheet margin, partly as a result of faster ice motion2,3,4. Surface melt waters can reach the base of the ice sheet and enhance basal ice motion5,6. However, the response of ice motion to seasonal variations in meltwater supply is poorly constrained both in space and time. Here we present ice motion data obtained with global positioning system receivers located along a ∼35 km transect at the western margin of the Greenland ice sheet throughout a summer melt season. Our measurements reveal substantial increases in ice velocity during summer, up to 220% above winter background values. These speed-up events migrate up the glacier over the course of the summer. The relationship between melt and ice motion varies both at each site throughout the melt season and between sites. We suggest that these patterns can be explained by the seasonal evolution of the subglacial drainage system similar to hydraulic forcing mechanisms for ice dynamics that have been observed at smaller glaciers.