Characterization of valid auxiliary functions for representations of extreme value distributions and their max-domains of attraction

In this paper we study two important representations for extreme value distributions and their max-domains of attraction (MDA), namely von Mises representation (vMR) and variation representation (VR), which are convenient ways to gain limit results. Both VR and vMR are defined via so-called auxiliary functions psi. Up to now, however, the set of valid auxiliary functions for vMR has neither been characterized completely nor separated from those for VR. We contribute to the current literature by introducing ''universal'' auxiliary functions which are valid for both VR and vMR representations for the entire MDA distribution families. Then we identify exactly the sets of valid auxiliary functions for both VR and vMR. Moreover, we propose a method for finding appropriate auxiliary functions with analytically simple structure and provide them for several important distributions.Comment: 33 page

Carbon cycling in an Arctic fjord (Scoresby Sund, East Greenland) with regard to the influence of glacial meltwater discharge

Greenland fjords receive considerable amounts of meltwater discharge from the Greenland Ice Sheet, influencing the physical and biogeochemical conditions within the fjords. Because ice melt will increase with ongoing climate change, research on present-day conditions is urgently needed to make better projections for the future. In the present study, a comprehensive analysis of the carbon cycle in Scoresby Sund, the world’s largest fjord system situated at the southeastern coast of Greenland, was conducted. In summer 2016, Scoresby Sund and its northernmost branch, Nordvestfjord, were visited. While the narrow Nordvestfjord is influenced by numerous marine-terminating glaciers and surface meltwater discharge, the wide Outer Scoresby Sund is much less affected by meltwater. Surface partial pressure of CO2, primary production, particulate organic carbon (POC) flux, and remineralisation within the water column are reported. The data reveal that meltwater significantly influenced the carbon dynamics within the fjord. First, meltwater itself increased the uptake of carbon dioxide from the atmosphere. Second, meltwater limited net community production in Nordvestfjord to 31 - 35 mmol C m-2 d-1 compared to the Outer Scoresby Sund and the shelf (43 - 67 mmol C m-2 d-1) by inhibiting the resupply of nutrients to the surface and by shadowing of silts contained in the meltwater. Finally, the POC flux close to glacier fronts was enhanced due to ballasting by silts, which diminished the remineralisation within the water column and increased the share of organic carbon that reached the sea floor. In Outer Scoresby Sund, by contrast, most remineralisation took place in the upper water column and particle concentrations below were mainly dependent on the present water mass. This study presents the first findings ever about biogeochemical cycling in Scoresby Sund. The results imply that Greenland fjords should be examined on a regional scale to highlight significant differences in carbon dynamics depending on the degree of meltwater discharge within a single fjord system

Cascading effects augment the direct impact of CO2 on phytoplankton growth in a biogeochemical model

Atmospheric and oceanic CO2 concentrations are rising at an unprecedented rate. Laboratory studies indicate a positive effect of rising CO2 on phytoplankton growth until an optimum is reached, after which the negative impact of accompanying acidification dominates. Here, we implemented carbonate system sensitivities of phytoplankton growth into our global biogeochemical model FESOM-REcoM and accounted explicitly for coccolithophores as the group most sensitive to CO2. In idealized simulations in which solely the atmospheric CO2 mixing ratio was modified, changes in competitive fitness and biomass are not only caused by the direct effects of CO2, but also by indirect effects via nutrient and light limitation as well as grazing. These cascading effects can both amplify or dampen phytoplankton responses to changing ocean pCO2 levels. For example, coccolithophore growth is negatively affected both directly by future pCO2 and indirectly by changes in light limitation, but these effects are compensated by a weakened nutrient limitation resulting from the decrease in small-phytoplankton biomass. In the Southern Ocean, future pCO2 decreases small-phytoplankton biomass and hereby the preferred prey of zooplankton, which reduces the grazing pressure on diatoms and allows them to proliferate more strongly. In simulations that encompass CO2-driven warming and acidification, our model reveals that recent observed changes in North Atlantic coccolithophore biomass are driven primarily by warming and not by CO2. Our results highlight that CO2 can change the effects of other environmental drivers on phytoplankton growth, and that cascading effects may play an important role in projections of future net primary production

Interaction matters: Bottom‐up driver interdependencies alter the projected response of phytoplankton communities to climate change

Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large-scale ocean biogeochemistry models mostly account for growth responses to each driver separately and leave the results of these experimental multiple-driver studies largely unused. Here, we amend phytoplankton growth functions in a biogeochemical model by dual-driver interactions (CO2 and temperature, CO2 and light), based on data of a published meta-analysis on multiple-driver laboratory experiments. The effect of this parametrization on phytoplankton biomass and community composition is tested using present-day and future high-emission (SSP5-8.5) climate forcing. While the projected decrease in future total global phytoplankton biomass in simulations with driver interactions is similar to that in control simulations without driver interactions (5%-6%), interactive driver effects are group-specific. Globally, diatom biomass decreases more with interactive effects compared with the control simulation (-8.1% with interactions vs. no change without interactions). Small-phytoplankton biomass, by contrast, decreases less with on-going climate change when the model accounts for driver interactions (-5.0% vs. -9.0%). The response of global coccolithophore biomass to future climate conditions is even reversed when interactions are considered (+33.2% instead of -10.8%). Regionally, the largest difference in the future phytoplankton community composition between the simulations with and without driver interactions is detected in the Southern Ocean, where diatom biomass decreases (-7.5%) instead of increases (+14.5%), raising the share of small phytoplankton and coccolithophores of total phytoplankton biomass. Hence, interactive effects impact the phytoplankton community structure and related biogeochemical fluxes in a future ocean. Our approach is a first step to integrate the mechanistic understanding of interacting driver effects on phytoplankton growth gained by numerous laboratory experiments into a global ocean biogeochemistry model, aiming toward more realistic future projections of phytoplankton biomass and community composition

Comparison of 'Mental training' and physical practice in the mediation of a structured facial examination : a quasi randomized, blinded and controlled study

Background: The correct performance of a structured facial examination presents a fundamental clinical skill to detect facial pathologies. However, many students are not adequately prepared in this basic clinical skill. Many argue that the traditional ‘See One, Do One’ approach is not sufficient to fully master a clinical skill. ‘Mental Training’ has successfully been used to train psychomotor and technical skills in sports and other surgical fields, but its use in Oral and Maxillofacial Surgery is not described. We conducted a quasi-experimental to determine if ‘Mental Training’ was effective in teaching a structured facial examination. Methods: Sixty-seven students were randomly assigned to a ‘Mental Training’ and ‘See One, Do One’ group. Both groups received standardized video instruction on how to perform a structured facial examination. The ‘See One, Do One’ group then received 60 min of guided physical practice while the ‘Mental Training’ group actively developed a detailed, stepwise sequence of the performance of a structured facial examination and visualized this sequence subvocally before practicing the skill. Student performance was measured shortly after (T1) and five to 10 weeks (T2) after the training by two blinded examiners (E1 and E2) using a validated checklist. Results: Groups did not differ in gender, age or in experience. The ‘Mental Training’ group averaged significantly more points in T1 (pE1 = 0.00012; pE2 = 0.004; dE1 = 0.86; dE2 = 0.66) and T2 (pE1 = 0.04; pE2 = 0.008, dE1 = 0.37; dE2 = 0.64) than the ‘See One, Do One’ group. The intragroup comparison showed a significant (pE1 = 0.0002; pE2 = 0.06, dE1 = 1.07; dE2 = 0.50) increase in clinical examination skills in the ‘See One, Do One’ group, while the ‘Mental Training’ group maintained an already high level of clinical examination skills between T1 and T2. Discussion: ‘Mental Training’ is an efficient tool to teach and maintain basic clinical skills. In this study ‘Mental Training’ was shown to be superior to the commonly used ‘See One, Do One’ approach in learning how to perform a structured facial examination and should therefore be considered more often to teach physical examination skills

"Wissenschaft fürs Wohnzimmer" – two years of interactive, scientific livestreams weekly on YouTube

Science communication is becoming increasingly important to connect academia and society, and to counteract fake news among climate change deniers. Online video platforms, such as YouTube, offer great potential for low-threshold communication of scientific knowledge to the general public. In April 2020 a diverse group of researchers from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research launched the YouTube channel "Wissenschaft fürs Wohnzimmer" (translated to "Sitting Room Science") to stream scientific talks about climate change and biodiversity every Thursday evening. Here we report on the numbers and diversity of content, viewers, and presenters from 2 years and 100 episodes of weekly livestreams. Presented topics encompass all areas of polar research, social issues related to climate change, and new technologies to deal with the changing world and climate ahead. We show that constant engagement by a group of co-hosts, and presenters from all topics, career stages, and genders enable a continuous growth of views and subscriptions, i.e. impact. After 783 days the channel gained 30,251 views and 828 subscribers and hosted well-known scientists while enabling especially early career researchers to improve their outreach and media skills. We show that interactive and science-related videos, both live and on-demand, within a pleasant atmosphere, can be produced voluntarily while maintaining high quality. We further discuss challenges and possible improvements for the future. Our experiences may help other researchers to conduct meaningful scientific outreach and to push borders of existing formats with the overall aim of developing a better understanding of climate change and our planet

Glacial meltwater effects on the carbon cycle of Scoresby Sund (Greenland), the world's largest fjord system

Climate change induced mass loss of the Greenland Ice Sheet increases the amount of meltwater, which is mainly released into the numerous fjords along the coast of Greenland. Due to its low salinity and high silt load, meltwater can profoundly affect the biogeochemical cycling of carbon. We visited the world’s largest fjord system, Scoresby Sund at the eastern coast of Greenland, and its northernmost branch, Nordvestfjord, in the summer of 2016 for investigating biogeochemical carbon cycling. The data reveal that meltwater limited the productivity by inhibiting the resupply of nutrients to the surface and by shadowing the upper part of the water column by the introduction of silts. These silts, though, increased the export of organic carbon to depth by ballasting the sinking organic particles. While the region close to the fjord entrance was influenced by shelf waters, the water column within Nordvestfjord was significantly modulated by meltwater input from a number of marine- and land-terminating glaciers. Our results show that there was a clear gradient from a productive system with efficient remineralization at the mouth of the fjord to a less productive system with a high carbon export towards the inner fjord parts. These results imply that Scoresby Sund can be seen as a hotspot of carbon burial