Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs

Dissertation (Ph.D.) University of Alaska Fairbanks, 2022Increased surface melt in the percolation zone of Greenland causes significant changes in the firn structure, directly affecting the surface mass balance of the ice sheet and the amount and timing of meltwater runoff. Thick impermeable layers, referred to as ice slabs, are preventing melt water percolation and refreezing in the firn favoring lateral movement of water and direct runoff to the oceans. The objective of this dissertation is to enhance the understanding of these processes by modeling the surface energy balance and resulting melt, and investigating the spatial and temporal changes in firn surface properties and associated water movement in the percolation zone in southwest Greenland. Extensive fieldwork was carried out in this region between 2017 and 2019, including a collection of 19 shallow firn cores at several sites and the operation of two weather stations. A surface-energy balance model was forced with automatic weather station data from two sites (2040 and 2360 m a.s.l.). Extensive model validation and sensitivity analysis reveal that the skin layer formulation used to compute the surface temperature by closing the energy balance leads to a consistent overestimation of melt by more than a factor of two or three depending on the site. The results indicate that the energy available for melt is highly sensitive to small changes in surface temperature and suggests caution is needed in modeling Greenland melt from weather data. Furthermore, the spatial and temporal variability in air temperature bias of two regional climate models, MAR and RACMO, is assessed over the entire ice sheet. Model results are compared to 35 automatic weather stations over more than 25 years. Both models perform well in the ablation zone ( 1500 m a.s.l.). The seasonal evolution and interannual variability of near-surface firn characteristics in the percolation zone of southwest Greenland can be tracked with Sentinel-2 optical imagery. Fully saturated seasonal snow (blue slush) and lateral movement of water are strongly correlated with local topography. Furthermore there is evidence of water movement from higher to lower elevations, following surface slope, even after the halting of melt in the second half of August. This suggests that the formation of ice slabs is a self-sustained feedback process increasing the efficiency of the runoff networks in the percolation zone. Ice slabs form and become thicker in areas with smaller surface slope than the surroundings where melt water ponds on top of the impermeable layer, flows, and refreezes during fall, adding to the ice slab. This dissertation provides useful insights on the processes driving ongoing changes in the percolation zone of Greenland due to global warming. However, several questions remain still open. Melt is the main driver of changes. Accurately modeling it, solving the uncertainties in observed and modeled sensible and ground heat flux, is essential. Furthermore, more ground truth and field observations are necessary in the region where blue slush forms on top of ice slabs to quantitatively determine how much water leaves the ice sheet and how much instead refreezes thickening the ice slabs.National Science Foundation (NSF Award #1603815)1. Introduction -- 2. Challenges in modeling the energy balance and melt in the percolation zone of the Greenland ice sheet -- 3 Spatio-temporal variability of regional climate models air temperature biases over the Greenland ice sheet -- 4. Spatio-temporal variations of blue slush and water flow in the percolation zone of Greenland: the role of local topography -- 5. Conclusions

Low ozone concentrations promote adipogenesis in human adipose-derived adult stem cells

Ozone is a strong oxidant, highly unstable atmospheric gas. Its medical use at low concentrations has been progressively increasing as an alternative/adjuvant treatment for several diseases. In this study, we investigated the effects of mild ozonisation on human adipose-derived adult stem (hADAS) cells i.e., mesenchymal stem cells occurring in the stromal-vascular fraction of the fat tissue and involved in the tissue regeneration processes. hADAS cells were induced to differentiate into the adipoblastic lineage, and the effect of low ozone concentrations on the adipogenic process was studied by combining histochemical, morphometric and ultrastructural analyses. Our results demonstrate that ozone treatment promotes lipid accumulation in hADAS without inducing deleterious effects, thus paving the way to future studies aimed at elucidating the effect of mild ozonisation on adipose tissue for tissue regeneration and engineering

Assessing precipitation mechanisms on Kilimanjaro and Mount Kenya : an idealized modeling study

Only in english.Tropical glaciers have proved to be fundamental in the understanding of the climate behaviour and its change in the tropical mid troposphere, where measurements have been only recently collected. Glaciers on Kilimanjaro and Mount Kenya in tropical East Africa are among the best studied sites in the tropics and their general behaviour is nowadays well understood. The two mountains, located 370 km away from each other, are often considered as typically influenced by the same air masses. Yet, their precipitation patterns and glaciers behaviour differ considerably. This indicates that either different air masses are at play or that precipitation processes are considerably different. The present study aims to investigate the most relevant mechanisms of precipitation over Kilimanjaro and Mount Kenya. First, in-situ observations and ERA-Interim reanalysis data are used to characterize the atmospheric background conditions during precipitation events at the two mountains. Next, idealized vertical profiles are constructed and used as an atmospheric reference state for simulations with the Weather Research and Forecasting (WRF) model. Two types of model topography are used, a semi-realistic topography constructed from a high-resolution digital elevation dataset (SRTM) and an ideal topography obtained by a parametric formula. A series of sensitivity simulations is carried out with modified topography, atmospheric reference state and surface heat fluxes to asses the dominant factors governing precipitation over the two mountains. The analysis of atmospheric background conditions confirms the hypothesis that Kilimanjaro and Mount Kenya are locally influenced by the same air mass during precipitation events. Numerical simulations show that the mesoscale circulation over the two mountains is the result of a complex interaction of the large-scale flow with the topography and the surface heat fluxes. Precipitation distribution and magnitude are very sensitive to the orientation of the mountain respect to the large-scale flow. Moreover the precipitation magnitude and the shift upslope, towards the summit, of the precipitation maximum are strongly controlled by the surface heat fluxes. With this, we aim to enhance the climate information from the differently behaving glaciers on the two East African mountains.by Federico CoviUniversity of Innsbruck, Masterarbeit, 2016Innsbruck, Univ., Masterarb., 2016(VLID)154247

Ozone treatment induces antioxidant stress response through Keap1/Nrf2 dependent pathway

Recently ozone therapy has been applied successfully as adjuvant therapy in the treatment of several disorders such as rheumatoid arthr\u131tis, heart and vascular disease, asthma emphysema and multiple sclerosis. Positive effects of ozone therapy have been hypothesized to rely on the capability of mild acute oxidative stress to induce antioxidant response. Nevertheless, molecular mechanisms behind those beneficial effects remain unclear. Some evidence suggests that mild oxidative stress induced by ozone treatments leads to activation of the transcription factor Nrf2 (nuclear factor erythroid-derived-like2). Nrf2 regulates the expression of genes under the control of antioxidant response element (ARE) enhancer. These genes include drug metabolizing enzymes, such as glutathione s-transferases (GSTs) and NAD(P)H-quinone Oxidoreductase 1 (NQO1), and antioxidant genes, such as heme oxygenase-1 (OH-1), the subunit of \u3b3-glutamylcysteine synthetase (\u3b3-GCS) and thioredoxin. Under basal conditions, Nrf2 is sequestered in the cytoplasm by its specific inhibitor Keap1 (Kelch-like ECH associated protein), which promotes Nrf2 ubiquitination and proteasomal degradation within a few minutes after its transcription. Under specific stimuli, Nrf2 dissociates from Keap1 and is preserved from degradation. Then, Nrf2 translocates into the nucleus, heterodimerizes with Maf proteins and trans-activates ARE-mediated genes. The current study was designed to investigate whether ozone therapy might induce ARE activation via Nrf2-dependent mechanisms. First, we established a HeLa cell line engineered to express NanoLuc Luciferase under the control of ARE promoter. We show that the treatment with different concentrations of ozone increased ARE-driven expression of NanoLuc in a dose- 413 dependent manner (Figure 1a). Ultrastructural immunocytochemistry showed Nrf2 to be associated to perichromatin fibrils, which are sites of active transcription (Figure 1b). Hela cells were transiently transfected with Nrf2-GFP and/or Keap1-dsRed fusion proteins to enable microscopy visualization of Nfr2 and Keap1 subcellular localization (Figure 2a). As expected, in untreated cells Nrf2-GFP disappeared when co-transfected with Keap1-dsRed. In contrast, ozone treatment induced persistence of Nrf2-GFP fluorescence and its massive nuclear translocation, suggesting that ozone might prevent Keap1-mediated Nrf2 degradation. In line with this conclusion we found an increased amount of Nrf2 protein compared to controls over 30 minutes after ozone treatment (Figure 2b), likely due to an increased Nrf2 stability. Finally, Keap1 transient overexpression partially reverted ARE-Luc activation in ozone treated cells (Figure 2c), thus providing further evidence that ozone treatment is able to induce an antioxidant stress response through a Keap1/Nrf2-dependent pathway

Shallow firn cores 1989 - 2019 in southwest Greenland’s percolation zone reveal decreasing density and ice layer volume after 2012

Abstract Refreezing of meltwater in firn is a major component of Greenland ice-sheet's mass budget, but in situ observations are rare. Here, we compare the firn density and total ice layer thickness in the upper 15 m of 19 new and 27 previously published firn cores drilled at 15 locations in southwest Greenland (1850–2360 m a.s.l.) between 1989 and 2019. At all sites, ice layer thickness covaries with density over time and space. At the two sites with the earliest observations (1989 and 1998), bulk density increased by 15–18%, in the top 15 m over 28 and 21 years, respectively. However, following the extreme melt in 2012, elevation-detrended density using 30 cores from all sites decreased by 15 kg m −3 a −1 in the top 3.75 m between 2013 and 2019. In contrast, the lowest elevation site's density shows no trend. Thus, temporary build-up in firn pore space and meltwater infiltration capacity is possible despite the long-term increase in Greenland ice-sheet melting

Reanalysis of a 10-year record (2004-2013) of seasonal mass balances at Langenferner/Vedretta Lunga, Ortler Alps, Italy

Records of glacier mass balance represent important data in climate science and their uncertainties affect calculations of sea level rise and other societally relevant environmental projections. In order to reduce and quantify uncertainties in mass balance series obtained by direct glaciological measurements, we present a detailed reanalysis workflow which was applied to the 10-year record (2004 to 2013) of seasonal mass balance of Langenferner, a small glacier in the European Eastern Alps. The approach involves a methodological homogenization of available point values and the creation of pseudo-observations of point mass balance for years and locations without measurements by the application of a process-based model constrained by snow line observations. We examine the uncertainties related to the extrapolation of point data using a variety of methods and consequently present a more rigorous uncertainty assessment than is usually reported in the literature. Results reveal that the reanalyzed balance record considerably differs from the original one mainly for the first half of the observation period. For annual balances these misfits reach the order of &gt; 300 kg m-2 and could primarily be attributed to a lack of measurements in the upper glacier part and to the use of outdated glacier outlines. For winter balances respective differences are smaller (up to 233 kg m-2) and they originate primarily from methodological inhomogeneities in the original series. Remaining random uncertainties in the reanalyzed series are mainly determined by the extrapolation of point data to the glacier scale and are on the order of ±79 kg m-2 for annual and ±52 kg m-2 for winter balances with values for single years/seasons reaching ±136 kg m-2. A comparison of the glaciological results to those obtained by the geodetic method for the period 2005 to 2013 based on airborne laser-scanning data reveals that no significant bias of the reanalyzed record is detectable.</p

Mild ozonisation activates antioxidant cell response by the Keap1/Nrf2 dependent pathway

Treatment with low-dose ozone is successfully exploited as an adjuvant therapy in the treatment of several disorders. Although the list of medical applications of ozone therapy is increasing, molecular mechanisms underlying its beneficial effects are still partially known. Clinical and experimental evidence suggest that the therapeutic effects of ozone treatment may rely on its capability to mount a beneficial antioxidant response through activation of the nuclear factor erythroid-derived-like 2 (Nrf2) pathway. However, a conclusive mechanistic demonstration is still lacking. Here, we bridge this gap of knowledge by providing evidence that treatment with a low concentration of ozone in cultured cells promotes nuclear translocation of Nrf2 at the chromatin sites of active transcription and increases the expression of antioxidant responsive element (ARE)-driven genes. Importantly, we show that ozone-induced ARE activation can be reverted by the ectopic expression of the Nrf2 specific inhibitor Kelch-like ECH associated protein (Keap1), thus proving the role of the Nrf2 pathway in the antioxidant response induced by mild ozonisation

Imaging techniques for the evaluation of grapes in withering for Amarone wine production

Optical imaging (OI) is an emerging field developed in recent years which can be a very versatile, fast and non-invasive approach for the acquisition of images of small (few centimetres) sized samples, such as layers of cells (in vitro), small animals (in vivo), animal organs (ex vivo) and innovative materials. OI was primarily developed for biomedical applications to study the progression of some pathologies and to assess the efficacy of new pharmaceutical compounds. Here we applied the OI technique to a completely new field: the study of food optical properties. In this case we exploited the optical properties of endogenous molecules, which are generally considered responsible of a background noise affecting the investigation. Here we used this sort of \u201cnoise\u201d, named autofluorescence, to obtain information on the drying of Corvinone grapes employed for Amarone wine production. OI can provide interesting information and, inserted in a multimodal approach, it may be a real support to other techniques in the description of a biological phenomenon