The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere-sea ice-ocean model

The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene Thermal Maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveal a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from a previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in a ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that the modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come

The impact of early Holocene Arctic Shelf flooding on climate in an atmosphere–ocean–sea–ice model

Glacial terminations are characterized by a strong rise in sea level related to melting ice sheets. This rise in sea level is not uniform all over the world, because regional effects (uplift and subsidence of coastal zones) are superimposed on global trends. During the early Holocene the Siberian Shelf became flooded before 7.5 ka BP and the coastline reached modern-day high stands at 5 ka BP. This area is currently known as a sea-ice production area and contributes significantly to the sea-ice exported from the Arctic through the Fram Strait. This leads to the following hypothesis: during times of rising sea levels, shelves become flooded, increasing sea-ice production on these shelves, increasing sea-ice volume and export through the Fram Strait and causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and fresher sea surface conditions. We have tested this hypothesis in an atmosphere–ocean–sea–ice coupled model of intermediate complexity (LOVECLIM). Our experiment on early Holocene Siberian Shelf flooding shows that in our model sea-ice production in the Northern Hemisphere increases (15%) and that sea-ice extent in the Northern Hemisphere increases (14%) but sea-ice export decreases (−15%) contrary to our hypothesis. The reason of this unexpected behaviour has its origin in a weakened polar vortex, induced by the land–ocean changes due to the shelf flooding, and a resulting decrease of zonality in the Nordic Seas pressure regime. Hence the winter Greenland high and the Icelandic low strengthen, yielding stronger winds on both sides of the Nordic Seas. Increased winds along the East Greenland Current support local sea-ice production and transport towards the South, resulting in a wider sea-ice cover and a southward shift of convection areas. The overall strength of the Atlantic meridional overturning circulation is reduced by 4% and the heat transport in the Atlantic basin by 7%, resulting in an annual cooling pattern over the Nordic Seas by up to −4 °C. We find that the flooding of the Siberian shelf resulting from an orbitally induced warming and related glacioeustatic sea level rise causes a Nordic Seas cooling feedback opposed to this warming

Sidewall depletion in nano-patterned LAO/STO heterostructures

We report the fabrication of nanostructures from the quasi-two-dimensional electron gas (q2DEG) formed at the LaAlO$_{3}$/ SrTiO$_{3}$ (LAO/STO) interface. The process uses electron beam lithography in combination with reactive ion etching. This technique allows to pattern high-quality structures down to lateral dimensions as small as $100$nm while maintaining the conducting properties without inducing conductivity in the STO substrate. Temperature dependent transport properties of patterned Hall bars of various widths show only a small size dependence of conductivity at low temperature as well as at room temperature. The deviation can be explained by a narrow lateral depletion region. All steps of the patterning process are fully industry compatible.Comment: 5 pages, 4 figure

Associations between stress and migraine and tension-type headache: Results from a school-based study in adolescents from grammar schools in Germany

Introduction: Stress is considered the major contributor to migraine and tension-type headache in adolescents. Previous studies have focused on general stressors, whereas the aim of the present study was to investigate associations between individuals’ stressful experiences and different types of headache. Methods: Adolescents from 10th and 11th grades of grammar schools filled in questionnaires. Stressful experiences were measured with the Trier Inventory of Chronic Stress. Type of headache was classified according to the International Classification of Headache Disorders. Linear regressions, adjusted for sex and grade, were calculated to estimate differences in stress scores that can be attributed to migraine, tension-type headache or miscellaneous headache. Results: A total of 1260 questionnaires were analysed. Tension-type headache, migraine and co-existing migraine plus tension-type headache were found in 48.7%, 10.2% and 19.8% of the participants. In subjects with migraine or co-existing migraine plus tension-type headache, high increases in stress scores were found in all investigated dimensions, whereas much weaker and inconsistent associations were found in subjects with tension-type headache only. Conclusions: The characteristic of migraine is more associated with stressful experiences than this is the case for tensiontype headache. This suggests that adolescent migraine patients might specially benefit from behavioural interventions regarding stress

Myofascial Trigger Points in Children With Tension-Type Headache: A New Diagnostic and Therapeutic Option

The goal of this pilot study was to evaluate the effect of a trigger point–specific physiotherapy on headache frequency, intensity, and duration in children with episodic or chronic tension-type headache. Patients were recruited from the special headache outpatient clinic. A total of 9 girls (mean age 13.1 years; range, 5-15 years) with the diagnosis of tension-type headache participated in the pilot study from May to September 2006 and received trigger point–specific physiotherapy twice a week by a trained physiotherapist. After an average number of 6.5 therapeutic sessions, the headache frequency had been reduced by 67.7%, intensity by 74.3%, and duration by 77.3%. No side effects were noted during the treatment. These preliminary findings suggest a role for active trigger points in children with tension-type headache. Trigger point–specific physiotherapy seems to be an effective therapy in these children. Further prospective and controlled studies in a larger cohort are warranted

Concurrent TNFRSF1A R92Q and pyrin E230K mutations in a child with multiple sclerosis

We report a 16-year-old female patient with a severe course of multiple sclerosis and concomitant symptoms suggestive of a hereditary autoinflammatory disease. Genetic analyses revealed that she inherited a TNFRSF1A R92Q mutation from her mother and a pyrin E230K mutation from her father. To our knowledge, this is the first report of a patient with severe childhood multiple sclerosis and mutations in two genes which predispose to hereditary autoinflammatory disorders. We speculate that these mutations contribute to early multiple sclerosis manifestation and enhance the inflammatory damage inflicted by the autoimmune response

Pretreatment and conversion of distiller's dried grains with solubles for acetone-butanol-ethanol (ABE) production

Distillers dried grains with solubles (DDGS) is a low-value co-product from dry grind ethanol production. Due to its high fiber content, DDGS is used primarily as a feed for ruminant animals. Conversion of the carbohydrate components in DDGS to biofuel would improve the overall economics of dry grind ethanol production. The effect of solids loading oil pretreatment of DDGS and oil subsequent acetone-butanol-ethanol (ABE) fermentation was examined. DDGS samples were subjected to six pretreatments, involving acidic and alkaline electrolyzed water, at three solids loadings (20%, 30%, and 40% w/w). After a 72 h hydrolysis, the highest glucose yield was obtained from the sulfuric acid pretreated samples. In fermentation tests using Clostridium acetobutylicum P260 for ABE production, the highest ABE concentration was similar to 17 g L-1, which was achieved from alkaline electrolyzed water pretreated samples at 30% (w/w) solids loading. The solids loading in a pretreatment significantly affected both the sugar yield from enzymatic hydrolysis and the ABE yield from fermentation of DDGS hydrolysates. The hydrolysate from alkaline electrolyzed water pretreatment at 30% (w/w) solids was found to be most favorable to ABE production, while that from sulfuric acid pretreatment was the least fermentable, although it produced the highest sugar yield

Self-reported muscle pain in adolescents with migraine and tension-type headache

Aim: To identify possible associations between muscular pain and headache in adolescents in a large population-based sample. Methods: Grammar school students were invited to fill in a questionnaire on headache and associated lifestyle factors. Headache was classified according to the German version of the International Classification of Headache Disorders (2nd edition). Muscular pain was assessed via denoting affected areas in schematic drawings of a body and via provoked muscular pain on controlled movements of head, neck and shoulder regions. Results: Prevalence of any headache within the previous 6 months exceeded 80%. In all subjects muscular pain or pain on movement was most prominent in the neck and shoulder region, ranging from 9% to 27% in the non-headache population to up to 63% for individuals with migraine or mixed migraine and tension-type headache (TTH). Frequency of muscular pain increased significantly with growing chronicity of TTH. Interpretation: A strong association between muscle pain in the neck/shoulder region and headache was observed, pointing to the importance of muscular pain for headache in adolescents. Also, in this age group muscular pain appears to be of particular importance in chronic TTH and – unexpectedly – in migraine, which is the most important new finding in our study

Long-term variations in Iceland–Scotland overflow strength during the Holocene

The overflow of deep water from the Nordic seas into the North Atlantic plays a critical role in global ocean circulation and climate. Approximately half of this overflow occurs via the Iceland–Scotland (I–S) overflow, yet the history of its strength throughout the Holocene (~ 0–11 700 yr ago, ka) is poorly constrained, with previous studies presenting apparently contradictory evidence regarding its long-term variability. Here, we provide a comprehensive reconstruction of I–S overflow strength throughout the Holocene using sediment grain size data from a depth transect of 13 cores from the Iceland Basin. Our data are consistent with the hypothesis that the main axis of the I–S overflow on the Iceland slope was shallower during the early Holocene, deepening to its present depth by ~ 7 ka. Our results also reveal weaker I–S overflow during the early and late Holocene, with maximum overflow strength occurring at ~ 7 ka, the time of a regional climate thermal maximum. Climate model simulations suggest a shoaling of deep convection in the Nordic seas during the early and late Holocene, consistent with our evidence for weaker I–S overflow during these intervals. Whereas the reduction in I–S overflow strength during the early Holocene likely resulted from melting remnant glacial ice sheets, the decline throughout the last 7000 yr was caused by an orbitally induced increase in the amount of Arctic sea ice entering the Nordic seas. Although the flux of Arctic sea ice to the Nordic seas is expected to decrease throughout the next century, model simulations predict that under high emissions scenarios, competing effects, such as warmer sea surface temperatures in the Nordic seas, will result in reduced deep convection, likely driving a weaker I–S overflow