Classification of calving fronts around Antarctica

Iceberg calving is the largest loss term in Antarctic mass balance. The iceberg areas vary from a few square meters (growler) to several hundred square kilometres (huge tabular icebergs or ice islands) and their shape (blocky, domed or tabular) depends on the morphology of their calving front. The Antarctic coastline has a length of about 18 000km and is characterized by a large spectrum of morphological properties. In contrast to the Greenland ice sheet, Antarctica is surrounded by a variety of large, medium and small sized ice shelves, besides of glacier tongues and parts without offshore floating ice masses. With the aid of synthetic aperture radar (SAR) images all ice shelves and glacier tongues around Antarctica were mapped. The mosaic of the RADARSAT-1 Antarctica Mapping Project (RAMP) Antarctic Mapping Mission 1 (AMM) was used at a 100 m x 100 m image resolution and the ice shelves were extracted by using the grounding line of the MODIS Mosaic of Antarctica (MOA) Project and the RAMP1-AMM coastline. An automated detection of crevasses was used as a first calving front classification. On the basis of the orientation of the crevasses to one another and relative to the calving front, and the distance between them, an estimation of the dominant size of potentially calving icebergs was made. Other parameters (e.g. shape of the calving front itself, pinning points) were used to make a clearer distinction between calving sites. The Antarctic coast is classified into several groups of calving sites e.g. no floating ice offshore (e.g. Mawson Coast), large ice shelf (e.g. Filcher-Ronne-Ice Shelf) or large glacier tongue (e.g. Mertz Glacier). The resulting map of the classified calving fronts around Antarctica and their description will be used to achieve a detailed picture of crevasse formation and propagation within a co-operation with material scientists and ice shelf modelers

Polar aircraft Polar5 and Polar6 operated by the Alfred Wegener Institute

Due to the remoteness and difficulty to access the snow covered polar regions, ski-equipped aircraft are an indispensable tool for polar research. The Alfred Wegener Institute has a long tradition in airborne polar science – starting with the aircraft Polar1 and Polar2 in 1983. In 2007 the first Basler BT-67 (Polar5) and in 2011 the second Basler BT-67 (Polar6) were brought into service and replaced Polar2 and Polar4. They carry a variety of scientific equipment for investigation of the lithosphere, atmosphere and cryosphere and all their interactions. Beside being deployed for science missions, the aircraft are also part of the Dronning Maud Land Air Network (DROMLAN), a logistical partnership to transport equipment and personnel to various stations in Dronning Maud Land, Antarctica

A Depolarization Ratio Anomaly Detector to identify icebergs in sea ice using dual-polarization SAR images

Icebergs represent hazards to maritime traffic and offshore operations. Satellite Synthetic Aperture Radar (SAR) is very valuable for the observation of polar regions and extensive work was already carried out on detection and tracking of large icebergs. However, the identification of small icebergs is still challenging especially when these are embedded in sea ice. In this work, a new detector is proposed based on incoherent dual-polarization SAR images. The algorithm considers the limited extension of small icebergs, which are supposed to have a stronger cross polarization and higher cross- over co-polarization ratio compared to the surrounding sea or sea ice background. The new detector is tested with two satellite systems. Firstly, RADARSAT-2 quad-polarimetric images are analyzed to evaluate the effects of high resolution data. Subsequently a more exhaustive analysis is carried out using dual-polarization ground detected Sentinel-1a Extra Wide swath images acquired over the time span of two months. The test areas are on the East Coast of Greenland, where several icebergs have been observed. A quantitative analysis and a comparison with a detector using only the cross polarization channel is carried out exploiting grounded icebergs as test targets. The proposed methodology improves the contrast between icebergs and sea ice clutter by up to 75 times. This returns an improved probability of detection

annual elevation change, a digital elevation model, and surface flow velocity

The polar ice sheets are unique paleoclimatic archives and play an important role in recent and future climate. The melting of the big freshwater reservoirs will not only increase the global sea level, but will also influence the ocean currents. Therefore, it will be of particular interest to improve the currently available numeric climate models to achieve more accurate statements about climatic change and its consequences. In this work, the evaluation and the different applications of GPS and altimetry data will be described in respect to enhance models. The antarctic area of investigation, Dronning Maud Land (DML), is of particular interest for German polar research, because both the overwintering station Neumayer and the summer station Kohnen are located within it. In the surroundings of these two stations, highly accurate kinematic GPS measurement were made, which will be the basis for the digital elevation model presented here. Because these data are spatially limited, they are supplemened with remotely sensed data. For this purpose, two airborne altimetry data sets and spaceborne laser altimetry data of the Ice, Cloud, and land Elevation Satellite (ICESat) are used...thesi

Neumayer III and Kohnen Station in Antarctica operated by the Alfred Wegener Institute

The Alfred Wegener Institute operates two stations in Dronning Maud Land, Antarctica. The German overwintering station Neumayer III is located on the Ekström Ice Shelf at 70°40’S and 08°16’W and is the logistics base for three long-term observatories (meteorology, air chemistry and geophysics) and nearby research activities. Due to the vicinity to the coast (ca. 20 km from the ice shelf edge), the Neumayer III Station is the junction for many German Antarctic expeditions, especially as the starting point for the supply traverse for the second German station Kohnen.The summer station Kohnen is located about 600 km from the coast and 750 km from Neumayer III Station on the Antarctic plateau at 75°S and 00°04’E. It was erected as the base for the deep-drilling ice core project, which took place between 2001 and 2006. Since then Kohnen Station is used as a logistics base for different research projects

With a little help from my friends? Acculturation and mental health in Arabic-speaking refugee youth living with their families

Introduction: Refugee youth are often faced with the compounding challenges of heightened exposure to traumatic events and acculturating to a new country during a developmental period when their sense of self is still forming. This study investigated whether refugee youth’s acculturation orientation (separation, integration, marginalization, and assimilation) is associated with depressive and posttraumatic stress symptoms and aimed to identify additional indicators of acculturation that may contribute to mental health. Methods: A total of 101 Arabic-speaking refugee youths (aged 14–20 years), who were living with their families and attending school in Germany, took part in the study. They answered questions concerning traumatic exposure and posttraumatic stress symptoms, depressive symptoms, and several indicators of acculturation, including cultural orientation, positive and negative intra- and intergroup contact, language skills and friendship networks. All participants were categorized into one of four acculturation orientations using median splits. Results: Kruskal–Wallis rank sum tests revealed that acculturation orientation was not significantly associated with depressive symptoms [χ2 (3, 97) = 0.519, p = 0.915] or posttraumatic stress symptoms [χ2 (3, 97) = 0.263, p = 0.967]. Regression analysis revealed that German language skills were significantly associated with lower scores of depressive symptoms (p = 0.016) and number of friends in Germany was significantly associated with lower scores of depressive (p = 0.006) and posttraumatic stress symptoms (p = 0.002), respectively. Discussion: Policies that provide refugee youth with access to language classes and social activities with peers do not only enable them to actively participate in a new society but may also have a positive effect on their mental health

Characterization of JG024, a pseudomonas aeruginosa PB1-like broad host range phage under simulated infection conditions

<p>Abstract</p> <p>Background</p> <p><it>Pseudomonas aeruginosa </it>causes lung infections in patients suffering from the genetic disorder Cystic Fibrosis (CF). Once a chronic lung infection is established, <it>P. aeruginosa </it>cannot be eradicated by antibiotic treatment. Phage therapy is an alternative to treat these chronic <it>P. aeruginosa </it>infections. However, little is known about the factors which influence phage infection of <it>P. aeruginosa </it>under infection conditions and suitable broad host range phages.</p> <p>Results</p> <p>We isolated and characterized a phage, named JG024, which infects a broad range of clinical and environmental <it>P. aeruginosa </it>strains. Sequencing of the phage genome revealed that the phage JG024 is highly related to the ubiquitous and conserved PB1-like phages. The receptor of phage JG024 was determined as lipopolysaccharide. We used an artificial sputum medium to study phage infection under conditions similar to a chronic lung infection. Alginate production was identified as a factor reducing phage infectivity.</p> <p>Conclusions</p> <p>Phage JG024 is a suitable broad host range phage which could be used in phage therapy. Phage infection experiments under simulated chronic lung infection conditions showed that alginate production reduces phage infection efficiency.</p