Sea-ice signatures in coherently reflected GNSS signals: Findings of the MOSAiC expedition

Sea ice is a crucial parameter in the Earth climate system. Its high albedo compared to water influences the oceans' radiation budget. The state of sea ice is highly variable due to seasonal change and global warming. GNSS reflectometry can contribute to global monitoring sea ice. Properties like ice salinity, temperature and thickness affect the signal reflection. The MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) gave the opportunity to conduct reflectometry measurements under different sea-ice conditions in the Arctic. A dedicated setup was mounted, in close cooperation with the Alfred-Wegener-Institute (AWI), on the German research icebreaker Polarstern that drifted during nine months with the Arctic sea ice. Here, results from the expedition's first leg in autumn 2019 are presented when the ship started drifting at about 85°N to 87°N in the Siberian Sector of the Arctic. Profiles of sea-ice reflectivity are derived with daily resolution considering reflection data recorded at left-handed (LH) and righthanded (RH) circular polarization. Respective predictions of reflectivity are provided assuming reflection models of bulk sea ice or a sea-ice slab. The later allows to include the effect of signal penetration down to the underlying water. Results of comparison between LH profiles and bulk model confirm that the reflectivity decreases (about 10 dB) when the ship goes into compact sea ice. In the central Arctic period anomaly signatures in observed reflectivity occur. The comparison of signatures and applied models (bulk and slab) indicate the role of coherent signal penetration into the ice. Salinity and temperature of sea ice have influence on these signatures. We conclude that estimation of ice type/salinity and temperature can profit from grazing angle GNSS reflectometry. Future studies will proceed to investigate these signatures in coherent observations

GNSS transpolar earth reflectometry exploriNg system (G-TERN): Mission concept

The global navigation satellite system (GNSS) Transpolar Earth Reflectometry exploriNg system (G-TERN) was proposed in response to ESA's Earth Explorer 9 revised call by a team of 33 multi-disciplinary scientists. The primary objective of the mission is to quantify at high spatio-temporal resolution crucial characteristics, processes and interactions between sea ice, and other Earth system components in order to advance the understanding and prediction of climate change and its impacts on the environment and society. The objective is articulated through three key questions. 1) In a rapidly changing Arctic regime and under the resilient Antarctic sea ice trend, how will highly dynamic forcings and couplings between the various components of the ocean, atmosphere, and cryosphere modify or influence the processes governing the characteristics of the sea ice cover (ice production, growth, deformation, and melt)? 2) What are the impacts of extreme events and feedback mechanisms on sea ice evolution? 3) What are the effects of the cryosphere behaviors, either rapidly changing or resiliently stable, on the global oceanic and atmospheric circulation and mid-latitude extreme events? To contribute answering these questions, G-TERN will measure key parameters of the sea ice, the oceans, and the atmosphere with frequent and dense coverage over polar areas, becoming a "dynamic mapper" of the ice conditions, the ice production, and the loss in multiple time and space scales, and surrounding environment. Over polar areas, the G-TERN will measure sea ice surface elevation (<10 cm precision), roughness, and polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability for 12 simultaneous observations. Unlike currently orbiting GNSS reflectometry missions, the G-TERN uses the full GNSS available bandwidth to improve its ranging measurements. The lifetime would be 2025-2030 or optimally 2025-2035, covering key stages of the transition toward a nearly ice-free Arctic Ocean in summer. This paper describes the mission objectives, it reviews its measurement techniques, summarizes the suggested implementation, and finally, it estimates the expected performance

Exploiting the Role of Endogenous Lymphoid-Resident Dendritic Cells in the Priming of NKT Cells and CD8+ T Cells to Dendritic Cell-Based Vaccines

Transfer of antigen between antigen-presenting cells (APCs) is potentially a physiologically relevant mechanism to spread antigen to cells with specialized stimulatory functions. Here we show that specific CD8+ T cell responses induced in response to intravenous administration of antigen-loaded bone marrow-derived dendritic cells (BM-DCs), were ablated in mice selectively depleted of endogenous lymphoid-resident langerin+ CD8α+ dendritic cells (DCs), suggesting that the antigen is transferred from the injected cells to resident APCs. In contrast, antigen-specific CD4+ T cells were primed predominantly by the injected BM-DCs, with only very weak contribution of resident APCs. Crucially, resident langerin+ CD8α+ DCs only contributed to the priming of CD8+ T cells in the presence of maturation stimuli such as intravenous injection of TLR ligands, or by loading the BM-DCs with the glycolipid α-galactosylceramide (α-GalCer) to recruit the adjuvant activity of activated invariant natural killer-like T (iNKT) cells. In fact, injection of α-GalCer-loaded CD1d−/− BM-DCs resulted in potent iNKT cell activation, suggesting that this glycolipid antigen can also be transferred to resident CD1d+ APCs. While iNKT cell activation per se was independent of langerin+ CD8α+ DCs, some iNKT cell-mediated activities were reduced, notably release of IL-12p70 and transactivation of NK cells. We conclude that both protein and glycolipid antigens can be exchanged between distinct DC species. These data suggest that the efficacy of DC-based vaccination strategies may be improved by the incorporation of a systemic maturation signal aimed to engage resident APCs in CD8+ T cell priming, and α-GalCer may be particularly well suited to this purpose

Role of the Chemokine Receptors CCR1, CCR2 and CCR4 in the Pathogenesis of Experimental Dengue Infection in Mice

Dengue virus (DENV), a mosquito-borne flavivirus, is a public health problem in many tropical countries. Recent clinical data have shown an association between levels of different chemokines in plasma and severity of dengue. We evaluated the role of CC chemokine receptors CCR1, CCR2 and CCR4 in an experimental model of DENV-2 infection in mice. Infection of mice induced evident clinical disease and tissue damage, including thrombocytopenia, hemoconcentration, lymphopenia, increased levels of transaminases and pro-inflammatory cytokines, and lethality in WT mice. Importantly, infected WT mice presented increased levels of chemokines CCL2/JE, CCL3/MIP-1α and CCL5/RANTES in spleen and liver. CCR1-/- mice had a mild phenotype with disease presentation and lethality similar to those of WT mice. In CCR2-/- mice, lethality, liver damage, levels of IL-6 and IFN-γ, and leukocyte activation were attenuated. However, thrombocytopenia, hemoconcentration and systemic TNF-α levels were similar to infected WT mice. Infection enhanced levels of CCL17/TARC, a CCR4 ligand. In CCR4-/- mice, lethality, tissue injury and systemic inflammation were markedly decreased. Despite differences in disease presentation in CCR-deficient mice, there was no significant difference in viral load. In conclusion, activation of chemokine receptors has discrete roles in the pathogenesis of dengue infection. These studies suggest that the chemokine storm that follows severe primary dengue infection associates mostly to development of disease rather than protection

City branding as economic necessity

Kvalitetno brendiranje grada je preduvjet za njihovu prepoznatljivost, kvalitetno pozicioniranje i stvaranje dodatne vrijednosti. Praksa i mnogobrojni primjeri potvrđuju ispravnost ove teze. Brendiranje gradova je nužno kako bi se pojačala konkurentnost, ostvarila veća dobit i osigurao razvoj mjesta. No ne radi se samo o ekonomskim kategorijama jer se pod razvojem mjesta podrazumijevaju i pozitivna demografska kretanja, obogaćivanje kulturnih sadržaja kao i drugih činitelja koji podižu ukupnu kvalitetu života. Izazov je to i nužnost i za gradove u Hrvatskoj kako bi bili konkurentni u oštroj tržišnoj konkurenciji.Quality city branding is a precondition for their recognazibility, quality positionig and creating of added value. Practice and numerous examples confirm correction of this theses. City branding is necessary to enhance concurence, gain bigger profit and ensure place development. But this is not only about economic categories because under place development it is understandable alsto positive demographic movement, enrichment of cultural contens as well as other factors which raise total quality of life. This is as well a challenge as it is a necessity for cities in Croatia so they could be concurente in harsh economy concurence

Reflectivity of second-year Arctic sea ice: Findings from the MOSAiC expedition

Sea ice is a crucial parameter of the Earth climate system. Its high albedo compared to water influences the oceans' radiation budget significantly. The importance of monitoring arises from the high variability of sea-ice state and amount induced by seasonal change and global warming. GNSS reflectometry can contribute to global monitoring of sea ice with high potential to extend the spatiotemporal coverage of today's observation techniques. Properties like ice salinity, temperature and thickness can affect the signal reflection. The MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) gave us the opportunity to conduct reflectometry measurements under different sea-ice conditions in the central Arctic. A dedicated setup was mounted, in close cooperation with the Alfred-Wegener-Institute (AWI), on the German research icebreaker Polarstern that drifted during nine months with the Arctic sea ice. We present results from the expedition's first leg in autumn 2019. They refer to the Siberian Sector of the Arctic (from about 85°N to 87°N). Profiles of sea-ice reflectivity over elevation angle (range: 1° to 45°) are derived with daily resolution considering reflection data recorded at left-handed (LH) and right-handed (RH) circular polarization. Respective predictions of reflectivity are based on reflection models of bulk sea ice or a sea-ice slab. The latter allows to include the effect of signal penetration down to the underlying water. Results of comparison between LH profiles and bulk model confirm a reflectivity decreases (about 10 dB) when surrounding water vanishes and the ship drifts in compact sea ice. Second-year ice was the primary ice type reported by ancillary observations for the drifting period of the ship (first leg). Based on the LH profiles, relative sea-ice permittivity is estimated, assuming a bulk medium. The results (typically below 3) indicate an old ice type (second-year or multiyear ice) in agreement with the ancillary observations. Some days with higher estimates (above 3) are found that can be related to periods of water presence after ice breaking, for example, induced by a storm in mid-November. The presence of second-year ice is accompanied by anomalies in the reflectivity profiles. These anomalies can be quantified by the slope of the profile at lowest elevation angles, below 10°. LH profiles, that are predicted using the bulk model, show a slope with a characteristic steep rise. The derived LH profiles, by contrast, present a variable slope (turning even from rise to fall). This variable slope agrees with slab model predictions and indicates the role of coherent signal penetration into the ice slab. Sea ice salinity and temperature can alter the anomaly. We conclude that monitoring of ice type/salinity and temperature can benefit from the presented method of reflectivity derivation. The on-going study of the MOSAiC data set will proceed with reflectivity estimation for the later ice season. Possible factors of signal disturbance, especially atmospheric effects, will be considered

Remote sensing using coherently reflected signals of Global Navigation Satellite Systems: Opportunities and Challenges

Signal reflection, in the sense of multipath, is one of the most critical error sources in precise radio-based navigation. Intensive research evolved during the last two decades to apply reflected signals of GNSS (Global Navigation Satellite Systems) for remote sensing (reflectometry) of ocean and land surfaces. We conducted a series of reflectometry experiments since 2010 to study the occurrence of coherent GNSS reflection and the radio wave's interaction with water and sea-ice surfaces. These studies, led by GFZ, comprised airborne and ship-based measurements. The airborne measurements were realized with a Zeppelin NT airship over Lake Constance, with the HALO (High Altitude Long range) research aircraft over the Mediterranean Sea and in cooperation with ULCO along the channel coast in Northern France using a gyrocopter aircraft. The ship-based measurements were conducted during expeditions of Norwegian research vessels (Lance, Kronprins Haakon), led by NPI, to Arctic sea ice in Fram Strait, Barents Sea and aboard the German research vessel Polarstern during the MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate) to the central Arctic. Two main objectives were defined for these investigations: on the one hand, to measure the carrier phase of the reflected signal for surface height retrieval and on the other hand to estimate reflected signal power as a parameter for sea-ice remote sensing. The results demonstrated that coherent GNSS reflections can be used to resolve variations of the water surface (geoid undulation and sea surface topography) and to resolve the permittivity contrast of sea ice under variable conditions (ice concentration and ice type). We will give a review on these experiments and the results in combination with a glance on the evolution of GNSS reflectometry research in general. Finally, challenges that arise for coherent signal requirement, e.g., due to surface roughness and atmospheric irregularities will be discussed

Sea Ice concentration derived from GNSS reflection measurements in Fram Strait

Reflection power derived from the global navigation satellite system (GNSS) observations and its sensitivity to sea-ice concentration are investigated in this article. A corresponding experiment has been conducted during the Fram Strait cruise of the Norwegian research vessel Lance in summer 2016. The dedicated setup with a GNSS Occultation Reflectometry Scatterometry (GORS) receiver and dual-polarization (left- and right-handed) antenna links recorded 1922 h of reflection events during the 20-day cruise of the ship. The antenna setup, mounted 25.0 m above the waterline, serves to acquire sea surface reflections at grazing angles below 30°. Within a 5-min coherent integration period, direct and reflected signal contributions can be separated. Except for the highest sea states, with roll angle changes of 20° peak to peak, the separation allows to retrieve the reflection power and quantifies it in cross-, co-, and cross-to-co-polar ratios. The sea-ice concentration is inverted from power ratios using a non-linear least-squares algorithm. Additional data on sea-ice concentration gathered by a watchman on the ship are used for validation. The inversion results have a 20% resolution in concentration and 3-h resolution in time. The validation shows that the cross- and cross-to-co-polar data are sensitive to the sea-ice concentration. The respective Pearson correlation of 0.75 and 0.67 further suggests studies to foster the application of the GNSS data for sea-ice reflectometry

Spatially resolved detection of small molecules from press‐dried plant tissue using MALDI imaging

Abstract Premise Matrix‐assisted laser desorption/ionization mass spectrometry imaging (MALDI‐MSI) is a chemical imaging method that can visualize spatial distributions of particular molecules. Plant tissue imaging has so far mostly used cryosectioning, which can be impractical for the preparation of large‐area imaging samples, such as full flower petals. Imaging unsectioned plant tissue presents its own difficulties in extracting metabolites to the surface due to the waxy cuticle. Methods We address this by using established delipidation techniques combined with a solvent vapor extraction prior to applying the matrix with many low‐concentration sprays. Results Using this procedure, we imaged tissue from three different plant species (two flowers and one carnivorous plant leaf). Material factorization analysis of the resulting data reveals a wide range of plant‐specific small molecules with varying degrees of localization to specific portions of the tissue samples, while facilitating detection and removal of signal from background sources. Conclusions This work demonstrates applicability of MALDI‐MSI to press‐dried plant samples without freezing or cryosectioning, setting the stage for spatially resolved molecule identification. Increased mass resolution and inclusion of tandem mass spectrometry are necessary next steps to allow more specific and reliable compound identification