An explanation for the dark region in the western melt zone of the Greenland ice sheet

The western part of the Greenland ice sheet contains a region that is darker than the surrounding ice. This feature has been analysed with the help of MODIS images. The dark region appears every year during the summer season and can always be found at the same location, which makes meltwater unlikely as the only source for the low albedos. Spectral information indicates that the ice in this region contains more debris than the ice closer to the margin. ASTER images reveal a wavy pattern in the darker ice. Based on these findings we conclude that ice, containing dust from older periods, is presently outcropping near the margin, leading to albedos lower than observed for the remaining ablation area. Therefore it can be concluded that the accumulation of meltwater is a result rather than a cause of the darkening

Controls on advance of tidewater glaciers: results from numerical modeling applied to Columbia Glacier

This is the published version, also available here: http://dx.doi.org/10.1029/2006JF000551.A one-dimensional numerical ice flow model is used to study the advance of a tidewater glacier into deep water. Starting with ice-free conditions, the model simulates glacier growth at higher elevations followed by advance on land to the head of the fjord. Once the terminus reaches a bed below sea level, calving is initiated. A series of simulations was carried out with various boundary conditions and parameterizations of the annual mass balance. The results suggest that irrespective of the calving criterion and accumulation rate in the catchment area, it is impossible for the glacier terminus to advance into deeper water (>300 m water depth) unless sedimentation at the glacier front is included. The advance of Columbia Glacier, Alaska, is reproduced by the model by including “conveyor belt” recycling of subglacial sediment and the formation of a sediment bank at the glacier terminus. Results indicate slow advance through the deep fjord and faster advance in shallow waters approaching the terminal moraine shoal and the mouth of the fjord

Comparison of the meteorology and surface energy balance at Storbreen and Midtdalsbreen, two glaciers in southern Norway

We compare 5 years of meteorological records from automatic weather stations (AWSs) on Storbreen and Midtdalsbreen, two glaciers in southern Norway, located approximately 120 km apart. The records are obtained from identical AWSs with an altitude difference of 120 m and cover the period September 2001 to September 2006. Air temperature at the AWS locations is found to be highly correlated, even with the seasonal cycle removed. The most striking difference between the two sites is the difference in wind climate. Midtdalsbreen is much more under influence of the large-scale circulation with wind speeds on average a factor 1.75 higher. On Storbreen, weaker katabatic winds are dominant. The main melt season is from May to September at both locations. During the melt season, incoming and net solar radiation are larger on Midtdalsbreen, whereas incoming and net longwave radiation are larger on Storbreen, primarily caused by thicker clouds on the latter. The turbulent fluxes are a factor 1.7 larger on Midtdalsbreen, mainly due to the higher wind speeds. Inter-daily fluctuations in the surface energy fluxes are very similar at the AWS sites. On average, melt energy is a factor 1.3 larger on Midtdalsbreen, a result of both larger net radiation and larger turbulent fluxes. The relative contribution of net radiation to surface melt is larger on Storbreen (76%) than on Midtdalsbreen (66%). As winter snow depth at the two locations is comparable in most years, the larger amount of melt energy results in an earlier disappearance of the snowpack on Midtdalsbreen and 70% more ice melt than on Storbreen. We compare the relative and absolute values of the energy fluxes on Storbreen and Midtdalsbreen with reported values for glaciers at similar latitudes. Furthermore, a comparison is made with meteorological variables measured at two nearby weather stations, showing that on-site measurements are essential for an accurate calculation of the surface energy balance and melt rate

Modelling job crafting behaviours: Implications for work engagement

In this study among 206 employees (103 dyads), we followed the job demands–resources approach of job crafting to investigate whether proactively changing one’s work environment influences employee’s (actor’s) own and colleague s (partner’s) work engagement. Using social cognitive theory, we hypothesized that employees would imitate each other’s job crafting behaviours, and therefore influence each other’s work engagement. Results showed that the crafting of social and structural job resources, and the crafting of challenge job demands was positively related to own work engagement, whereas decreasing hindrance job demands was unrelated to own engagement. As predicted, results showed a reciprocal relationship between dyad members’ job crafting behaviours – each of the actor’s job crafting behaviours was positively related to the partner’s job crafting behaviours. Finally, employee’s job crafting was related to colleague’s work engagement through colleague’s job crafting, suggesting a modelling process

Mental Disorder During Adolescence:Evidence of Arrested Personality Development

The experience of a mental disorder may affect the development of personality in multiple ways, but empirical evidence regarding psychopathology effects on personality development that persist after remission of the disorder is limited and inconsistent. In the longitudinal cohort TRacking Adolescents' Individual Lives Survey (TRAILS), mental disorders during adolescence were assessed using the Composite International Diagnostic Interview and parent-reported effortful control, fearfulness, and frustration at age 11 and age 19 through the Early Adolescent Temperament Questionnaire. We found that adolescent mental disorders had small effects on personality change. Internalizing disorders predicted increases of fearfulness and frustration but hardly affected effortful control; externalizing disorders were unrelated to frustration and fearfulness but predicted a decrease of effortful control. Whereas fearfulness and frustration partially caught up after disorder remission, virtually all delay in effortful control was still present 2.9 years later, suggesting scarring effects

The association of developmental trajectories of adolescent mental health with early-adult functioning

BACKGROUND: Mental health problems during adolescence may create a problematic start into adulthood for affected individuals. Usually, categorical indicators of adolescent mental health issues (yes/no psychiatric disorder) are used in studies into long-term functional outcomes. This however does not take into account the full spectrum of mental health, nor does it consider the trajectory of mental health problem development over time. The aim of this study was twofold: (1) to identify distinct developmental trajectories of (co-occurring) internalizing and externalizing mental health symptoms over the course of adolescence (ages 11-19), and (2) to document the associations between these adolescent trajectories and economic, social, and health outcomes in young adulthood (age 22), unadjusted and adjusted for childhood functioning, putative confounders and current mental health. METHODS: Data were used from the Dutch TRAILS cohort study (subsample n = 1524, 47.3% males). Self-reported INT and EXT symptoms using the Youth/Adult Self Report were assessed four times (ages 11y, 13y, 16y, 19y). Adolescent mental health trajectories were estimated using Parallel-Processes Latent Class Growth Analyses. Self-reported economic, social, and health outcomes and parent-reported current mental health (using Adult Behaviour Checklist) were assessed at age 22. Multiple logistic regression analyses were performed to test associations between trajectories and outcomes. RESULTS: Four distinct trajectory classes were identified: (1) a normative class with decreasing-low INT+EXT symptoms (n = 460), (2) continuous moderately-high INT+EXT (n = 298), (3) continuous moderate, INT>EXT (n = 414), and (4) decreasing moderate, EXT>INT (n = 352). Compared to the normative class, the other three trajectories generally predicted less optimal early-adult outcomes, with the strongest effects observed for individuals with continuous moderate-high levels of both INT and EXT symptoms throughout adolescence. The associations largely remained after adjustment for pre-adolescent functioning, selected confounders and current mental health. CONCLUSIONS: Both adolescent trajectories and current mental health had substantial independent effects on early-adult functioning

Coupling of climate models and ice sheet models by surface mass balance gradients: application to the Greenland Ice Sheet

It is notoriously difficult to couple surface mass balance (SMB) results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation from a climate model, and parameterizing the meltwater run-off as a function of temperature, which is often related to surface elevation (<i>H</i><sub>s</sub>). In this study, we propose a new strategy to calculate SMB, to allow a direct adjustment of SMB to a change in ice sheet topography and/or a change in climate forcing. This method is based on elevational gradients in the SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation, using pairs of <i>H</i><sub>s</sub> and SMB within a minimum search radius. The continuously adjusting SMB forcing is consistent with climate model forcing fields, also for initially non-glaciated areas in the peripheral areas of an ice sheet. When applied to an asynchronous coupled ice sheet – climate model setup, this method circumvents traditional temperature lapse rate assumptions. Here we apply it to the Greenland Ice Sheet (GrIS). Experiments using both steady-state forcing and glacial-interglacial forcing result in realistic ice sheet reconstructions

Does the cognitive architecture of simplex and multiplex ASD families differ?

Contains fulltext : 167741.pdf (publisher's version ) (Open Access)Children with an autism spectrum disorder (ASD) and their unaffected siblings from 54 simplex (SPX, one individual in the family affected) and 59 multiplex (MPX, two or more individuals affected) families, and 124 controls were assessed on intelligence, social cognition and executive functions. SPX and MPX ASD probands displayed similar cognitive profiles, but within-family contrasts were highest in SPX families, suggesting SPX-MPX stratification may help parse etiological heterogeneity of ASD. Unaffected siblings (regardless SPX or MPX) were mostly unimpaired, suggesting that cognitive problems may be part of the defining features of ASD, rather than being an endophenotypic trait. Except for affective prosody, which appeared to be the most sensitive cognitive marker for detecting familial risk for ASD

Partitioning of melt energy and meltwater fluxes in the ablation zone of the west Greenland ice sheet

We present four years (August 2003–August 2007) of surface mass balance data from the ablation zone of the west Greenland ice sheet along the 67° N latitude circle. Sonic height rangers and automatic weather stations continuously measured accumulation/ablation and near-surface climate at distances of 6, 38 and 88 km from the ice sheet margin at elevations of 490, 1020 and 1520 m a.s.l. Using a melt model and reasonable assumptions about snow density and percolation characteristics, these data are used to quantify the partitioning of energy and mass fluxes during melt episodes. The lowest site receives very little winter accumulation, and ice melting is nearly continuous in June, July and August. Due to the lack of snow accumulation, little refreezing occurs and virtually all melt energy is invested in runoff. Higher up the ice sheet, the ice sheet surface freezes up during the night, making summer melting intermittent. At the intermediate site, refreezing in snow consumes about 10% of the melt energy, increasing to 40% at the highest site. The sum of these effects is that total melt and runoff increase exponentially towards the ice sheet margin, each time doubling between the stations. At the two lower sites, we estimate that radiation penetration causes 20–30% of the ice melt to occur below the surface