Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet

Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents and Norwegian seas where grounded ice sheets led to thickening of the gas hydrate stability zone during the last glaciation. The onset of methane release was coincident with deglaciation-induced pressure release and thinning of the hydrate stability zone. Methane efflux continued for 7–10 kyr, tracking hydrate stability changes controlled by relative sea-level rise, bottom water warming and fluid pathway evolution in response to changing stress fields. The protracted nature of seafloor methane emissions probably attenuated the impact of hydrate dissociation on the climate system

Fear causes tears - Perineal injuries in home birth settings. A Swedish interview study

<p>Abstract</p> <p>Background</p> <p>Perineal injury is a serious complication of vaginal delivery that has a severe impact on the quality of life of healthy women. The prevalence of perineal injuries among women who give birth in hospital has increased over the last decade, while it is lower among women who give birth at home. The aim of this study was to describe the practice of midwives in home birth settings with the focus on the occurrence of perineal injuries.</p> <p>Methods</p> <p>Twenty midwives who had assisted home births for between one and 29 years were interviewed using an interview guide. The midwives also had experience of working in a hospital delivery ward. All the interviews were tape-recorded and transcribed. Content analysis was used.</p> <p>Results</p> <p>The overall theme was "No rushing and tearing about", describing the midwives' focus on the natural process taking its time. The subcategories 1) preparing for the birth; 2) going along with the physiological process; 3) creating a sense of security; 4) the critical moment and 5) midwifery skills illuminate the management of labor as experienced by the midwives when assisting births at home.</p> <p>Conclusions</p> <p>Midwives who assist women who give birth at home take many things into account in order to minimize the risk of complications during birth. Protection of the woman's perineum is an act of awareness that is not limited to the actual moment of the pushing phase but starts earlier, along with the communication between the midwife and the woman.</p

Land, Environmental Externalities and Tourism Development

In a two sectors dynamic model we analyze the process of tourism development based on the accumulation of capital (building of tourism facilities) and the reallocation of land from traditional activities to the tourism sector. The model incorporates the conflict between occupation of the territory by the tourism facilities, other productive activities and availability of cultural, natural and environmental assets that are valued by residents and visitors. We characterize the process of tourism development in two settings: the socially optimal solution and a situation where the costs of tourism expansion are external to the decision makers, where externalities on residents as well as intraindustry externalities are considered. Regarding the optimal solution, we show that it is optimal to limit tourism expansion before it reaches its maximum capacity even in a context where the economic attractiveness of tourism relative to other productive sectors rise continuously. However, in this context and when all the costs of tourism development are externalities the only limit to tourism quantitative expansion is its maximum capacity determined by the availability of land. Finally, we show that excessive environmental degradation from the future generations' point of view is not a problem of discounting the future but rather a problem of externalities that affects negatively the current and future generations

Reduction and Stabilization of Plutonium Nitrate in Cation Exchange Feed and Product Solutions

In the conceutration and purification of Pu by cation exchange, the feed solution must be in the plus three valence state, but the nitrate solution from a solvent extraction process contains a high% of Pu/sup 4+/ and a small amount of Pu/sup 6+/. It was desired to find a reducing agent satisfactory for the reduction of Pu/sup 4+/ and Pu/sup 6+/ in Purex product streams and to make these streams suitable as cation exchange feed. The bisulfates met the requirements for speed and completeness of reduction in the feed material. (J.E.D.

Structural controls on seepage of thermogenic and microbial methane since the last glacial maximum in the Harstad Basin, southwest Barents Sea

The Harstad Basin is a structural block on the continental shelf of SW Barents Sea where gas hydrates likely occurred below the grounded ice-sheet during the last glaciation and it hosts active gas seepage at numerous seafloor sites. We present an integrated study of fluid flow systems in the Harstad Basin by combining seismic profile interpretations and gas flare mapping data with the geochemical results obtained on seafloor seeping gas and methane-derived carbonate crusts. More than 190 acoustic gas flares were registered in water column, many of them in association with pockmarks and carbonate crust fields. However, weak or absent seepage observed during remotely operated underwater vehicle transects across many pockmarks and crust fields suggests that seepage activity may have decreased since the last deglaciation. In the western Harstad Basin, seeps of microbial methane occur mainly above Tertiary formations that are pinching out below the glacial sediments. High amplitude seismic anomalies suggest the presence of gas pockets at the base of the glacial sediments and within Tertiary deposits. In contrast, gas seeping in the eastern Harstad Basin originates from a biodegraded thermogenic source tentatively connected to the deeply faulted Mesozoic rocks occurring below glacial sediments. This spatial variability in fluid sources is also recorded in the carbon isotope data of seafloor carbonate crusts, with δ13C values typically between −55 and −42‰ and −40 and −20 ‰VPDB for carbonate crusts associated with microbial and thermogenic fluids, respectively. U-Th chronology combined with the stable isotope data suggests that this discrepancy in fluid sources over a distance of about 20 km has been stable since the last glaciation and highlights the significance of regional underlying geology in mediating fluid supply to the seafloor