Greenland meltwater storage in firn limited by near-surface ice formation

Approximately half of Greenland’s current annual mass loss is attributed to runoff from surface melt1. At higher elevations, however, melt does not necessarily equal runoff, because meltwater can refreeze in the porous near-surface snow and firn2. Two recent studies suggest that all3 or most3, 4 of Greenland’s firn pore space is available for meltwater storage, making the firn an important buffer against contribution to sea level rise for decades to come3. Here, we employ in situ observations and historical legacy data to demonstrate that surface runoff begins to dominate over meltwater storage well before firn pore space has been completely filled. Our observations frame the recent exceptional melt summers in 2010 and 2012 (refs 5,6), revealing significant changes in firn structure at different elevations caused by successive intensive melt events. In the upper regions (more than ~1,900 m above sea level), firn has undergone substantial densification, while at lower elevations, where melt is most abundant, porous firn has lost most of its capability to retain meltwater. Here, the formation of near-surface ice layers renders deep pore space difficult to access, forcing meltwater to enter an efficient7 surface discharge system and intensifying ice sheet mass loss earlier than previously suggested3

Measurement of decline of functioning in persons with amyotrophic lateral sclerosis: responsiveness and possible applications of the Functional Independence Measure, Barthel Index, Rehabilitation Activities Profile and Frenchay Activities Index.

Contains fulltext : 50613.pdf (publisher's version ) (Closed access)It is important not only to monitor the functional change during the course of ALS, but also to determine whether or not the available help is sufficient. This study was performed to determine which generic assessment instrument is most appropriate. A multicentre cohort of patients with ALS was followed for one year. At baseline, six months, and 1 year four instruments were used: Functional Independence Measure (FIM), Rehabilitation Activities Profile (RAP), Barthel Index (BI), and Frenchay Activities Index (FAI). The responsiveness of the measures was examined using effect sizes and standardized response mean statistics. Seventy-three patients at baseline, 63 after six months and 43 after one year were assessed. If calculated on the group that completed all three assessments, the FIM, BI, and RAP showed moderate effect sizes and standardized response means over a period of six months and large effect sizes over 12 months. Based on their responsiveness FIM, BI, and RAP can be used to evaluate limitations in activities and care needs of persons with ALS and to evaluate treatment results in trials. The FIM was the most responsive instrument, although the BI might be easier to use in clinical practice