| 1. |
- Beaudon, Emilie, et al.
(author)
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Spatial and temporal variability of net accumulation from shallow cores from Vestfonna ice cap (Nordaustlandet, Svalbard)
- 2011
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In: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93:4, s. 287-299
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Journal article (peer-reviewed)abstract
- We analyse ice cores from Vestfonna ice cap (Nordaustlandet, Svalbard). Oxygen isotopic measurements were made on three firn cores (6.0, 11.0 and 15.5 m deep) from the two highest summits of the glacier located on the SW–NE and NW–SE central ridges. Sub-annual δ18O cycles were preserved and could be counted visually in the uppermost parts of the cores, but deeper layers were affected by post-depositional smoothing. A pronounced δ18O minimum was found near the bottom of the three cores. We consider candidates for this δ18O signal to be a valuable reference horizon since it is also seen elsewhere in Nordaustlandet. We attribute it to isotopically depleted snow precipitation, which NCEP/NCAR reanalysis shows was unusual for Vestfonna, and came from northerly air during the cold winter of 1994/95. Finding the 1994/95 time marker allows establishment of a precise depth/age scale for the three cores. The derived annual accumulation rates indirectly fill a geographical gap in mass balance measurements and thus provide information on spatial and temporal variability of precipitation over the glacier for the period spanned by the cores (1992–2009). Comparing records at the two locations also reveals that the snow net accumulation at the easternmost part of Vestfonna was only half of that in the western part over the last 17 years.
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| 2. |
- Braun, Matthias, et al.
(author)
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Changes of glacial front positions of Vestfonna (Nordaustlandet, Svalbard)
- 2011
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In: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93:4, s. 301-310
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Journal article (peer-reviewed)abstract
- Glaciers in Svalbard have shown considerable mass loss in recent years with a reported acceleration in the western and southern parts of the archipelago. However, for the ice cap Vestfonna, in northeastern Svalbard, climatic mass balance modelling has suggested almost balanced conditions over a period of nine years (2000–2009). A slightly positive geodetic mass balance (1990–2005) has been reported from a comparison of laser altimetry to older DEMs. A heterogeneous situation has been depicted for the various catchments, and hence changes in glacier extent can reveal additional information of glacier status, in particular when dealing with surge-type glaciers. We analysed a 34-year data record of multi-spectral satellite imagery in order to study changes in glacier frontal positions of the ice cap Vestfonna. A consistent pattern of almost steady retreat of the southern and north-eastern outlet glaciers of the ice cap is observed while Franklinbreen, the only major outlet glacier draining towards the north-west shows re-advance. This is consistent with an observed speed up and potential upcoming surge of this outlet. The glacier retreat on the southern coast also agrees with ICESat elevation change measurements. However, due to the glacier response time no direct relations between frontal retreat and surface mass balance can be drawn from the short observation period. The heterogeneous pattern of changes with on-going dynamic adjustments in some areas make the ice cap Vestfonna an ideal test site for future monitoring activities including novel techniques like differential interferometry from bi-static SAR systems.
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| 3. |
- Chrysafi, Anna, et al.
(author)
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Quantifying Earth system interactions for sustainable food production via expert elicitation
- 2022
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In: Nature Sustainability. - : Springer Science and Business Media LLC. - 2398-9629. ; 5:10, s. 830-842
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Journal article (peer-reviewed)abstract
- Several safe boundaries of critical Earth system processes have already been crossed due to human perturbations; not accounting for their interactions may further narrow the safe operating space for humanity. Using expert knowledge elicitation, we explored interactions among seven variables representing Earth system processes relevant to food production, identifying many interactions little explored in Earth system literature. We found that green water and land system change affect other Earth system processes strongly, while land, freshwater and ocean components of biosphere integrity are the most impacted by other Earth system processes, most notably blue water and biogeochemical flows. We also mapped a complex network of mechanisms mediating these interactions and created a future research prioritization scheme based on interaction strengths and existing knowledge gaps. Our study improves the understanding of Earth system interactions, with sustainability implications including improved Earth system modelling and more explicit biophysical limits for future food production.
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| 4. |
- Falk, Yana Znamenskaya, et al.
(author)
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Interactions of Perfluorohexyloctane With Polyethylene and Polypropylene Pharmaceutical Packaging Materials.
- 2020
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In: Journal of Pharmaceutical Sciences. - : Elsevier. - 0022-3549 .- 1520-6017. ; 109:7, s. 2180-2188
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Journal article (peer-reviewed)abstract
- Semifluorinated alkanes (SFAs) are aprotic solvents, which may be used as drug solvents for topical ocular applications, for instance, in dry eye syndrome. Their physical properties suggest that they might be prone to interaction with plastic materials, such as, polyethylene (PE) and polypropylene (PP), which are commonly used as packaging materials for pharmaceutical products. In this study, we investigate interactions of PE and PP with a liquid SFA perfluorohexyloctane (PFHO) using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross-polarized light microscopy. Binary phase diagrams of PFHO-PE and PFHO-PP systems demonstrating interactions of PFHO with the polymeric materials were constructed based on DSC data. According to this data, PFHO tends to lower the melting temperatures of PE and PP. The equilibrium values of solubilities of the polymers in PFHO and PFHO in the polymers were obtained by extrapolation of melting enthalpy data. Absorption of PFHO by PE and PP materials at ambient conditions after four weeks of equilibration was also studied by TGA. From the presented results, it may be concluded that thorough studies of interactions of PE or PP with SFAs are required when these materials are used as packaging components in SFA-based formulations.
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| 5. |
- Hamm, Alexandra, et al.
(author)
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Intercomparison of Gridded Precipitation Datasets over a Sub-Region of the Central Himalaya and the Southwestern Tibetan Plateau
- 2020
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In: Water. - : MDPI AG. - 2073-4441. ; 12:11
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Journal article (peer-reviewed)abstract
- Precipitation is a central quantity of hydrometeorological research and applications. Especially in complex terrain, such as in High Mountain Asia (HMA), surface precipitation observations are scarce. Gridded precipitation products are one way to overcome the limitations of ground truth observations. They can provide datasets continuous in both space and time. However, there are many products available, which use various methods for data generation and lead to different precipitation values. In our study we compare nine different gridded precipitation products from different origins (ERA5, ERA5-Land, ERA-interim, HAR v2 10 km, HAR v2 2 km, JRA-55, MERRA-2, GPCC and PRETIP) over a subregion of the Central Himalaya and the Southwest Tibetan Plateau, from May to September 2017. Total spatially averaged precipitation over the study period ranged from 411 mm (GPCC) to 781 mm (ERA-Interim) with a mean value of 623 mm and a standard deviation of 132 mm. We found that the gridded products and the few observations, with few exceptions, are consistent among each other regarding precipitation variability and rough amount within the study area. It became obvious that higher grid resolution can resolve extreme precipitation much better, leading to overall lower mean precipitation spatially, but higher extreme precipitation events. We also found that generally high terrain complexity leads to larger differences in the amount of precipitation between products. Due to the considerable differences between products in space and time, we suggest carefully selecting the product used as input for any research application based on the type of application and specific research question. While coarse products such as ERA-Interim or ERA5 that cover long periods but have coarse grid resolution have previously shown to be able to capture long-term trends and help with identifying climate change features, this study suggests that more regional applications, such as glacier mass-balance modeling, require higher spatial resolution, as is reproduced, for example, in HAR v2 10 km.
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| 6. |
- Jänicke, Britta, et al.
(author)
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Towards a city-wide analysis of mean radiant temperature at high spatial resolution – An example from Berlin, Germany
- 2015
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In: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
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Conference paper (other academic/artistic)abstract
- Heat stress is expected to increase in the future due to global climate change. Many epidemiological studies show the close link between elevated air temperature and increased morbidity and mortality, which are not restricted to subtropical and tropical regions but also common in cities at higher latitudes like Berlin (52.5° N). Heat-stress risks are particularly high in urban regions, since urban climate modifications of regional weather conditions tend to increase heat-stress hazards. In order to analyse heat-stress risks and hazards within a city, the mean radiant temperature is an important variable as it sums up long- and short-wave radiation that reaches the human body. Thus, the mean radiant temperature along with air temperature, atmospheric humidity and wind speed is used for the calculation of many biometeorological indices. In urban environments mean radiant temperature is highly variable due to the shadow patterns of objects. To calculate the mean radiant temperature, urban structures such as trees, bushes, courtyards, street canyons and buildings need to be parameterized or explicitly included. The former reduces the computation demand, but limits the possibility to derive planning measures to reduce heat stress. In addition, weather and climate influence the variability of the mean radiant temperature, because the atmospheric conditions are heterogeneous in large urban areas. Therefore, the aim of this study is to calculate the mean radiant temperature for the case of Berlin while considering both micro-scale urban structures and meso-scale atmospheric conditions. For the computation of the mean radiant temperature we apply a version of the SOLWEIG model (Lindberg et al. 2011) that is able to use gridded meteorological input data. Digital surface models of buildings and vegetation with a spatial resolution of 1m provide the height of the micro-scale urban structures. The Central Europe Refined analysis (CER) serves as input for meso-scale atmospheric conditions. We will discuss the resulting spatio-temporal pattern of the mean radiant temperature in view of the applied methodology as well as regarding actions to reduce heat stress.
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| 7. |
- Jänicke, Britta, et al.
(author)
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Towards city-wide, building-resolving analysis of mean radiant temperature
- 2016
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In: Urban Climate. - : Elsevier BV. - 2212-0955. ; 15, s. 83-98
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Journal article (peer-reviewed)abstract
- This study presents a method to simulate Tmrt building-resolving while considering both micro-scale urban structures and meso-scale atmospheric conditions. We extended the model SOLWEIG, one of the few methods to derive mean radiant temperature (Tmrt) building-resolved and city-wide, to include spatial patterns of meteorological input. Based on a day within an extreme heat event (2003) in Berlin, Germany, we examined the effect of the new method on Tmrt, which uses gridded meteorological input data from a mesoscale weather model, compared to a standard set-up using ungridded data. Results indicted a considerable effect of spatially resolved air temperature (up to 3.2 K) during midnight. Furthermore, we detected high sensitivity of Tmrt to the partitioning of direct and diffuse short-wave radiation. The spatial pattern of Tmrt revealed that at midday the city centre exhibited low values compared to open areas. We conclude that considering meso-scale atmospheric conditions and urban structure for simulating Tmrt city-wide can lead to a more appropriate description of heat-stress hazards and might also be valuable for climate-sensitive urban planning.
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| 8. |
- Lin, Qian, et al.
(author)
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Impacts of Bias-Corrected ERA5 Initial Snow Depth on Dynamical Downscaling Simulations for the Tibetan Plateau
- 2021
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In: Journal of Geophysical Research: Atmospheres. - 2169-897X .- 2169-8996. ; 126:23
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Journal article (peer-reviewed)abstract
- The Tibetan Plateau (TP) is often called the “Water Tower of Asia,” which contains the largest amount of snow and glaciers outside the polar regions. As an important and variable feature of the land surface, snow coverage on the TP has great impacts on regional climate. However, the commonly used ERA5 reanalysis in dynamical downscaling largely overestimates the snow depth for the TP. To improve the representation of snow cover in ERA5, a new ERA5-driven downscaling data set (High Asia Refined analysis version 2, HAR v2) was generated by the Weather Research and Forecasting (WRF) model with the bias-corrected snow depth. This study aims to identify and better understand the impact of bias-corrected initial snow conditions on simulated regional climate, by comparing the HAR v2 with a 5-year ERA5 forced WRF simulation without bias correction of initial snow depth (referred to as WRF_ERA5). The results show that the bias correction significantly improves the simulation of 2m air temperature (T2), with regional mean cold bias reduced by 0.2°C–2.4°C, but no significant improvement in precipitation simulation is found. Further comparative analysis reveals that higher snow depth in WRF_ERA5 leads to T2, mean daily precipitation, summer extreme precipitation, and contributions of convective precipitation to summer mean daily precipitation decrease by 0°C–4°C, 0%–60%, 0%–40%, and 0%–10%, respectively, in most areas of the TP. In addition, the bias-corrected initial snow depth also has impacts on simulated diurnal cycles of precipitation and T2 and leads to peak hours one hour earlier. Overall, this study confirms the importance of snow cover for the climate in the TP.
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| 9. |
- Lind, Tania K., et al.
(author)
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Effects of ethylene oxide chain length on crystallization of polysorbate 80 and its related compounds
- 2021
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In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 592, s. 468-484
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Journal article (peer-reviewed)abstract
- As a result of the synthesis protocol polyoxyethylene sorbitan monooleate (polysorbate 80, PS80) is a highly complex mixture of compounds. PS80 was therefore separated into its main constituents, e.g. polyoxyethylene isosorbide esters and polyoxyethylene esters, as well as mono- di- and polyesters using preparative high-performance liquid chromatography. In this comprehensive study the individual components and their ethoxylation level were verified by matrix assisted laser desorption/ionization time-of-flight and their thermotropic behavior was analyzed using differential scanning calorimetry and X-ray diffraction. A distinct correlation was found between the average length of the ethylene oxide (EO) chains in the headgroup and the individual compounds' ability to crystallize. Importantly, a critical number of EO units required for crystallization of the headgroup was determined (6 EO units per chain or 24 per molecule). The investigation also revealed that the hydrocarbon tails only crystallize for polyoxyethylene sorbitan esters if saturated. PS80 is synthesized by reacting with approximately 20 mol of EO per mole of sorbitol, however, the number of EO units in the sorbitan ester in commercial PS80 products is higher than the expected 20 (5 EO units per chain). The complex behavior of all tested compounds revealed that if the amount of several of the linear by-products is reduced, the number of EO units in the chains will stay below the critical number and the product will not be able to crystallize by the EO chains.
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| 10. |
- Moeller, Marco, et al.
(author)
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Snowpack Characteristics of Vestfonna and De Geerfonna (Nordaustlandet, Svalbard) : A Spatiotemporal Analysis Based on Multiyear Snow-Pit Data
- 2011
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In: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93A:4, s. 273-285
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Journal article (peer-reviewed)abstract
- Extensive glaciological field measurements were carried out on the ice cap Vestfonna as well as on the minor ice body De Geerfonna (Nordaustlandet, Svalbard) within the framework of IPY Kinnvika. Field campaigns were conducted during the period 20072010 in spring (April/May) and summer (August). In this study we compile and present snow cover information obtained from 22 snow pits that were dug on Vestfonna during this period. Locations are along two transects on the northwestern, land terminating slope of the ice cap, on its central summit, Ahlmann Summit, and at a set of several other locations in the eastern and northern part of the ice cap. Snow-cover information acquired from four snow pits on adjacent De Geerfonna is also incorporated in this study. Field data are analysed regarding snow stratigraphy, snow density, snow hardness and snow temperature. Results reveal mean snow densities of around 400 kg m-3 for the snowpack of Vestfonna with no apparent spatial or interannual variability. A distinctly higher value of more than 450 kg m-3 was obtained for De Geerfonna. A spatial comparison of snow water equivalents above the previous end-of-summer surface serves for obtaining insights into the spatial distribution of snow accumulation across Vestfonna. Altitude was found to be the only significant spatial parameter for controlling snow accumulation across the ice cap.
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