Thermo-insulation effect of a seasonal snow-cover on permafrost soil in Bayelva, Svalbard (1998 - 2017)

Bayelva is a high-arctic research site on Spitsbergen Island in the Svalbard archipelago (78.551N; 11.571E) where climate, soil and snow components are recorded since 1998 by the Alfred-Wegener-Institute. This study site is underlain by permafrost with average temperatures around -2 °C and seasonally snow-covered from October to May. The thermal insulation by the snow-pack decouples the soil temperatures from air temperature. To gain better understanding of the thermal relationships, analysis of long-term measurements of air temperature, radiation, soil temperature, and snow characteristics were examined in this study. Mean annual air temperature has increased by 0.14 °C per year for the period from 1998 to 2016 which is higher than the global average temperature change in the same period. Radiation balance trend analyses are characterized by an increase in long-wave radiation during winter months. Results of our snow characteristic studies show that the last day in the year with snow cover has been moving to earlier dates with 0.5 days per year (from 1998 to 2016), extending the snow-free season, thus resulting in more time for soil warming. This corresponds well with warming trends of all soil temperature sensors as well as the thickening of the active layer (ALT), which is estimated to have reached a depth of 2 m in 2016 for the first time. Since it is difficult to measure the exact ALT, we used the Stefan model for an estimate. To account for different magnitudes of insulation, an effective snow depth (Sdep,eff) was calculated for each year. High Sdep,eff values represent high thermo-insulation, due to early snowfall and long snow depths over 0.4 m, and can be linked to years in which re-freezing of the whole active layer took until early March of the next year. Our results support the importance of snow physical characteristics for the permafrost thermal regime, as also detailed in the Arctic Monitoring and Assessment Programme - an Arctic Council Working Group

Warming trends in Permafrost and thermo-insulation effect of a seasonal snow-cover on permafrost soil in Bayelva, Svalbard (1998 - 2017)

Permafrost around the Arctic is warming and thawing. We report data from the high arctic research site Bayelva (78.551N; 11.571E) located close to Ny-Alesund. Data on meteorology, energy balance components and subsur- face observations have been made for the last 20 years (1998-2017; Boike et al. 2017). This study site is underlain by permafrost with current mean permafrost temperature of -2.8◦C and is seasonally snow-covered from October to May. Mean annual, summer and winter soil temperature data at all depths have beenrising over the period of record with a warming trend of 0.18±0.07◦C/year in active layer and top of permafrost. However, interannual to sub-decadal variability is evident in the data and results mostly from differences of theclimate during the winter months. The modeled active layer thickness using the Stefan equation has increasedcontinuously from about 1m in 1998 and is estimated to have surpassed 2 m in 2016. The data show that snow ablation has started earlier, thus extending the snow free season, potentially re-sulting in more time for soil warming and deepening of active layer. The snow cover onset and ablation, aswell as the thermo insulation properties of the snow cover, will be investigated together with active layer and permafrost variables (temperature, volumetric water content) for further understanding of the observed warming and deepening. Boike, J., Juszak, I., Lange, S., Chadburn, S., Burke, E., Overduin, P. P., Roth, K., Ippisch, O., Bornemann, N., Stern, L., Gouttevin, I., Hauber, E., and Westermann, S.: A 20-year record (1998–2017) of permafrost, active layer and meteorological conditions at a high Arctic permafrost research site (Bayelva, Spitsbergen), Earth Syst. Sci. Data, 10, 355-390, https://doi.org/10.5194/essd-10-355-2018, 2018

A Computational Model of Trust-, Pupil-, and Motivation Dynamics

Autonomous machines are in the near future likely to increasingly interact with humans, and carry out their functions outside controlled settings. Both of these developments increase the requirements of machines to be trustworthy to humans. In this work, we argue that machines may also benefit from being able to explicitly build or withdraw trust with specific humans. The latter is relevant in situations where the integrity of an autonomous system is compromised, or if humans display untrustworthy behaviour towards the system. Examples of systems that could benefit might be delivery robots, maintenance robots, or autonomous taxis. This work contributes by presenting a biologically plausible model of unconditional trust dynamics, which simulates trust building based on familiarity, but which can be modulated by painful and gentle touch. The model displays interactive behaviour by being able to realistically control pupil dynamics, as well as determine approach and avoidance motivation

DMAP-[2.2]paracyclophane: Observation of an Unusual C-C Insertion

International audienc

Circulation of a Meaban-like virus in yellow-legged gulls and seabird ticks in the western Mediterranean Basin

In recent years, a number of zoonotic flaviviruses have emerged worldwide, and wild birds serve as their major reservoirs. Epidemiological surveys of bird populations at various geographical scales can clarify key aspects of the eco-epidemiology of these viruses. In this study, we aimed at exploring the presence of flaviviruses in the western Mediterranean by sampling breeding populations of the yellow-legged gull (Larus michahellis), a widely distributed, anthropophilic, and abundant seabird species. For 3 years, we sampled eggs from 19 breeding colonies in Spain, France, Algeria, and Tunisia. First, ELISAs were used to determine if the eggs contained antibodies against flaviviruses. Second, neutralization assays were used to identify the specific flaviviruses present. Finally, for colonies in which ELISA-positive eggs had been found, chick serum samples and potential vectors, culicid mosquitoes and soft ticks (Ornithodoros maritimus), were collected and analyzed using serology and PCR, respectively. The prevalence of flavivirus-specific antibodies in eggs was highly spatially heterogeneous. In northeastern Spain, on the Medes Islands and in the nearby village of L'Escala, 56% of eggs had antibodies against the flavivirus envelope protein, but were negative for neutralizing antibodies against three common flaviviruses: West Nile, Usutu, and tick-borne encephalitis viruses. Furthermore, little evidence of past flavivirus exposure was obtained for the other colonies. A subset of the Ornithodoros ticks from Medes screened for flaviviral RNA tested positive for a virus whose NS5 gene was 95% similar to that of Meaban virus, a flavivirus previously isolated from ticks of Larus argentatus in western France. All ELISA-positive samples subsequently tested positive for Meaban virus neutralizing antibodies. This study shows that gulls in the western Mediterranean Basin are exposed to a tick-borne Meaban-like virus, which underscores the need of exploring the spatial and temporal distribution of this flavivirus as well as its potential pathogenicity for animals and humans

Increasing the Reactivity of Nitrogen Catalysts

International audienc