Insulation effects of Icelandic dust and volcanic ash on snow and ice

In the Arctic region, Iceland is an important source of dust due to ash production from volcanic eruptions. In addition, dust is resuspended from the surface into the atmosphere as several dust storms occur each year. During volcanic eruptions and dust storms, material is deposited on the glaciers where it influences their energy balance. The effects of deposited volcanic ash on ice and snow melt were examined using laboratory and outdoor experiments. These experiments were made during the snow melt period using two different ash grain sizes (1 phi and 3.5 phi) from the Eyjafjallajokull 2010 eruption, collected on the glacier. Different amounts of ash were deposited on snow or ice, after which the snow properties and melt were measured. The results show that a thin ash layer increases the snow and ice melt but an ash layer exceeding a certain critical thickness caused insulation. Ash with 1 phi in grain size insulated the ice below at a thickness of 9-15 mm. For the 3.5 phi grain size, the insulation thickness is 13 mm. The maximum melt occurred at a thickness of 1 mm for the 1 phi and only 1-2 mm for 3.5 phi ash. A map of dust concentrations on Vatnajokull that represents the dust deposition during the summer of 2013 is presented with concentrations ranging from 0.2 up to 16.6 g m(-2).Peer reviewe

Textures, fabrics and meltlayer stratigraphy in the Hans Tausen ice core, North Greenland - indications of late Holocene ice cap genration? in: (U.C. Hammer, ed.) The Hans Tausen Ice Cap Glaciology and Glacial Geology

A thin section study of crystal structure has been carried out on a 345 m long ice core drilled to bedrock on Hans Tausen Iskappe, 1995. In addition a meltlayer stratigraphy was set up, showing how the fraction of meltlayer-ice in the core increases with depth. Main characteristics of crystal structure are increasing mean crystal size from top to bottom in the core and development of a weak single maximum c-axis fabric. The rate of ice crystal growth in the well dated upper half of the core is much lower than expected from studies of the normal grain growth regime in other polar ice cores. Probablythe grain boundary movements are impeded by impurities, which are present in relatively high concentrations in the Hans Tausen ice. Asuming the applicability of the calculated growth rate throughout the core, a late Holocene origin of the oldest ice is suggested by the size of the crystals close to the bedrock.Presented data furthermore implies that bottom ice temperatures were never near the melting point and it is concluded that there was no ice cap on the Hans Tausen plarteau earlier in Holocene

Haemostatic effect of aprotinin during craniosynostotic surgery in children.

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.BACKGROUND: Aprotinin has been used in our hospital since the year 2003 to reduce bleeding during craniosynostotic surgery in children. The aim of this retrospective study was to investigate its effect, primarily on bleeding and secondarily on the need for transfusion. METHODS: Thirteen children were treated with aprotinin from 2003 to 2008, while 39 were not treated in the period 1993-2002. Information on blood loss and need for transfusion during the operations in all 52 children was collected from their medical records. RESULTS: There was a significant difference in both blood loss and need for transfusion. Estimated blood volume was used to correct for difference in the children's age and size. In the aprotinin group, blood loss was 3.9% of circulating blood volume vs. 22.0%, and the need for transfusion was 0.0% vs. 21.1%. CONCLUSION: Blood loss and need for blood transfusion were significantly reduced in the aprotinin group. No allergic or other possible aprotinin-specific complications were registered in the aprotinin group