Algunas contribuciones tefrocronológicas a la vulcanología y glaciología de Islandia

Fil: Thorarinsson, S.. Universidad de Islandi

Satellite Geological and Geophysical Remote Sensing of Iceland. Vatnajoekull Area, Iceland: New Volcanic and Structural Features on ERTS-1 Imagery

There are no author-identified significant results in this report

UTILIZATION OF THE ICELANDIC COD STOCK IN A MULTISPECIES CONTEXT

The purpose of this paper is to discuss rules for deciding Total Allowable Catch (TAC) for Icelandic cod. For this purpose, a bioeconomic model describing harvesting and processing of cod, capelin, and shrimp in the Icelandic marine ecosystem is constructed and estimated. The model is used to analyze the probable effects of harvesting strategies on biomass, catch, and economic benefits from the exploitation of these species. Simulations are used to investigate probability profiles of biological and economic variables, taking into account inaccuracies in assessments and uncertainties in predictions. Optimal harvesting strategies are also investigated using a deterministic version of the model and taking into account problems of unemployment, overcapacity, and aversion to fluctuations in consumption. The analysis shows that it is beneficial to reduce fishing from the cod stock in order to allow the stock to recover to its optimum size. This increase in the cod stock will result in big decreases in the catch of capelin and shrimp.Resource /Energy Economics and Policy,

Satellite geological and geophysical remote sensing of Iceland: Preliminary results from analysis of MSS imagery

A binational, multidisciplinary research effort in Iceland is directed at an analysis of MSS imagery from ERTS-1 to study a variety of geologic, hydrologic, oceanographic, and agricultural phenomena. A preliminary evaluation of available MSS imagery of Iceland has yielded several significant results - some of which may have direct importance to the Icelandic economy. Initial findings can be summarized as follows: (1) recent lava flows can be delineated from older flows at Askja and Hekla; (2) MSS imagery from ERTS-1 and VHRR visible and infrared imagery from NOAA-2 recorded the vocanic eruption on Heimaey, Vestmann Islands; (3) coastline changes, particularly changes in the position of bars and beaches along the south coast are mappable; and (4) areas covered with new and residual snow can be mapped, and the appearance of newly fallen snow on ERTS-1, MSS band 7 appears dark where it is melting. ERTS-1 imagery provides a means of updating various types of maps of Iceland and will permit the compilation of special maps specifically aimed at those dynamic environmental phenomena which impact on the Icelandic economy

Survival of the Mýrdalsjökull ice cap through the Holocene thermal maximum: evidence from sulphur contents in Katla tephra layers (Iceland) from the last ∼8400 years

International audienceThe climate in Iceland was drier and warmer during the Holocene thermal maximum than it is today and it has been suggested that ice caps disappeared entirely. Katla, a volcano covered by the Mýrdalsjökull ice cap in southern Iceland, has erupted rather steadily throughout the Holocene. Preand post-eruption sulphur concentrations in its products have been determined in previous studies, through melt inclusions trapped in phenocrysts (pre-eruption mean values of 2155 ± 165 ppm) and fully degassed magmatic tephra (post-eruption mean values of 445 ± 130 ppm). The phreatomagmatic tephra has much more variable S contents (550-1775 ppm) and spans the compositional gap between magmatic tephra and melt inclusions. These variable sulphur values are attributed to arresting of degassing as the magma is quenched upon contact with external water in the shallow levels of the volcano conduit. Sulphur in Katla tephra can thus be used to evaluate whether Mýrdalsjökull survived the warm spells of the Holocene. In this study, sulphur concentrations in tephra layers representing the last ∼8400 years of the volcano's eruption history were measured, revealing concentrations in the phreatomagmatic range (600-1600 ppm). Hence, we conclude that over the last ∼8400 years, explosive activity at Katla has been dominated by phreatomagmatic eruptions, implying that the Mýrdalsjökull ice cap has been present throughout the Holocene

Satellite geological and geophysical remote sensing of Iceland: Preliminary results of geologic, hydrologic, oceanographic, and agricultural studies with ERTS-1 imagery

The author has identified the following significant results. The wide variety of geological and geophysical phenomena which can be observed in Iceland, and particularly their very direct relation to the management of the country's natural resources, has provided great impetus to the use of ERTS-1 imagery to measure and map the dynamic natural phenomena in Iceland. MSS imagery is being used to study a large variety of geological and geophysical eruptive products, geologic structure, volcanic geomorphology, hydrologic, oceanographic, and agricultural phenomena of Iceland. Some of the preliminary results from this research projects are: (1) a large number of geological and volcanic features can be studied from ERTS-1 imagery, particularly imagery acquired at low sun angle, which had not previously been recognized; (2) under optimum conditions the ERTS-1 satellite can discern geothermal areas by their snow melt pattern or warm spring discharge into frozen lakes; (3) various maps at scales of 1:1 million and 1:500,000 can be updated and made more accurate with ERTS-1 imagery; (4) the correlation of water reserves with snowcover can improve the basis for planning electrical production in the management of water resources; (5) false-color composites (MSS) permitted the mapping of four types of vegetation: forested; grasslands, reclaimed, and cultivated areas, and the seasonal change of the vegetation, all of high value to rangeland management

Breast reconstructive surgery: Risk factors for complications and health-related quality of life - Clinical studies

Background: Breast cancer is the most common form of cancer in women worldwide. Although the incidence is increasing, the mortality rate is not. This results in a growing number of breast cancer survivors, and thereby in increasing demand for breast reconstructions. Complications after breast reconstructive surgery are common and can be caused by a wide range of factors, such as the reconstructive method, perioperative factors and patient-related factors. As the principal aim of breast reconstruction is to reverse the mastectomy deformity and restore body image and health-related quality of life (HR-QoL), traditional clinical outcome measures, such as medical or surgical complications, do not suffice assessing the values of different reconstruction methods for the patient. There are no established guidelines on choosing the best reconstruction method for the individual patient. However, patient perspectives and experiences are important when choosing the reconstructive method, and HR-QoL needs to be investigated in a systematic way when comparing different reconstruction methods. Aim: The aim of this thesis is to evaluate postoperative complications, to find independent risk factors for complications and compare HR-QoL between breast reconstruction patients, and with the general population. Method: The four retrospective studies are based on a large database of breast reconstructions between the years 2003 and 2009 at the Department of Plastic Surgery, Sahlgrenska University Hospital, and results of HR-QoL questionnaires from patients surgically treated with breast reconstruction during this time. Results: Paper I states the importance of a systematic and meticulous registration of complications in comparisons of different methods. The study revealed high complication rates with all of the methods, and the spectrum of complications was related to the operation method, where the DIEP group had the highest rate. The pattern of occurrence of complications ranged between early and late time points. Paper II shows the perioperative factors of duration of surgery and blood loss during surgery as independent risk factors for several postoperative complications, both early and late. Paper III shows several patient-related factors and adjuvant therapy as independent risk factors for complications, such as BMI, smoking, and radiotherapy. Paper IV shows that patients reconstructed with a DIEP flap are more satisfied with their reconstruction and overall outcome than patients in the other groups. Conclusion: Complications after breast reconstructive surgery are common and can be caused by many different factors. Patients reconstructed with a DIEP flap are more satisfied with their reconstruction than patients reconstructed with other methods. To maximize patient satisfaction, DIEP flaps should be more widely available, and complications rate after this type of surgery should be minimized

Ecosystem recharge by volcanic dust drives broad-scale variation in bird abundance

Across the globe, deserts and volcanic eruptions produce large volumes of atmospheric dust, and the amount of dust is predicted to increase with global warming. The effects of long-distance airborne dust inputs on ecosystem productivity are potentially far-reaching but have primarily been measured in soil and plants. Airborne dust could also drive distribution and abundance at higher trophic levels, but opportunities to explore these relationships are rare. Here we use Iceland's steep dust deposition gradients to assess the influence of dust on the distribution and abundance of internationally important ground-nesting bird populations. Surveys of the abundance of breeding birds at 729 locations throughout lowland Iceland were used to explore the influence of dust deposition on bird abundance in agricultural, dry, and wet habitats. Dust deposition had a strong positive effect on bird abundance across Iceland in dry and wet habitats, but not in agricultural land where nutrient levels are managed. The abundance of breeding waders, the dominant group of terrestrial birds in Iceland, tripled on average between the lowest and highest dust deposition classes in both wet and dry habitats. The deposition and redistribution of volcanic materials can have powerful impacts in terrestrial ecosystems and can be a major driver of the abundance of higher trophic-level organisms at broad spatial scales. The impacts of volcanic ash deposition during eruptions and subsequent redistribution of unstable volcanic materials are strong enough to override effects of underlying variation in organic matter and clay content on ecosystem fertility. Global rates of atmospheric dust deposition are likely to increase with increasing desertification and glacier retreat, and this study demonstrates that the effects on ecosystems are likely to be far-reaching, both in terms of spatial scales and ecosystem components