TY - JOUR A1 - Wang, Qiong A1 - Smith, Joel A. A1 - Skroblin, Dieter A1 - Steele, Julian A. A1 - Wolff, Christian Michael A1 - Caprioglio, Pietro A1 - Stolterfoht, Martin A1 - Köbler, Hans A1 - Turren-Cruz, Silver-Hamill A1 - Li, Meng A1 - Gollwitzer, Christian A1 - Neher, Dieter A1 - Abate, Antonio T1 - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells JF - Solar RRL N2 - Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells. KW - cesium lead halides KW - crystal orientation KW - inorganic perovskites KW - ISOS-L-1I protocol KW - phase purity KW - photostability Y1 - 2020 VL - 4 IS - 9 PB - WILEY-VCH CY - Weinheim ER - TY - JOUR A1 - Samson, Stephanie A1 - Rech, Jeromy A1 - Perdigón-Toro, Lorena A1 - Peng, Zhengxing A1 - Shoaee, Safa A1 - Ade, Harald A1 - Neher, Dieter A1 - Stolterfoht, Martin A1 - You, Wei T1 - Organic solar cells with large insensitivity to donor polymer molar mass across all acceptor classes JF - ACS applied polymer materials N2 - Donor polymer number-average molar mass (M-n) has long been known to influence organic photovoltaic (OPV) performance via changes in both the polymer properties and the resulting bulk heterojunction morphology. The exact nature of these M-n effects varies from system to system, although there is generally some intermediate M-n that results in optimal performance. Interestingly, our earlier work with the difluorobenzotriazole (FTAZ)-based donor polymer, paired with either N2200 (polymer acceptor) or PC61BM (fullerene acceptor), PcBm demonstrated <10% variation in power conversion efficiency and a consistent morphology over a large span of M-n (30 kg/mol to over 100 kg/mol). Would such insensitivity to polymer M-n still hold true when prevailing small molecular acceptors were used with FTAZ? To answer this question, we explored the impact of FTAZ on OPVs with ITIC, a high-performance small-molecule fused-ring electron acceptor (FREA). By probing the photovoltaic characteristics of the resulting OPVs, we show that a similar FTAZ mn insensitivity is also found in the FTAZ:ITIC system. This study highlights a single-donor polymer which, when paired with an archetypal fullerene, polymer, and FREA, results in systems that are largely insensitive to donor M. Our results may have implications in polymer batch-to-batch reproducibility, in particular, relaxing the need for tight M-n control during synthesis. KW - polymer solar cells KW - conjugated polymers KW - fullerenes KW - fluorination KW - molecular weight KW - non-fullerene acceptors KW - power conversion efficiency Y1 - 2020 U6 - https://doi.org/10.1021/acsapm.0c01041 SN - 2637-6105 VL - 2 IS - 11 SP - 5300 EP - 5308 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Schulze, Patricia S. C. A1 - Bett, Alexander J. A1 - Bivour, Martin A1 - Caprioglio, Pietro A1 - Gerspacher, Fabian M. A1 - Kabaklı, Özde Ş. A1 - Richter, Armin A1 - Stolterfoht, Martin A1 - Zhang, Qinxin A1 - Neher, Dieter A1 - Hermle, Martin A1 - Hillebrecht, Harald A1 - Glunz, Stefan W. A1 - Goldschmidt, Jan Christoph T1 - 25.1% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1197 KW - heterojunction silicon solar cells KW - interfaces KW - perovskite solar cells KW - tandem solar cells KW - thin films Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525668 SN - 1866-8372 IS - 7 ER - TY - JOUR A1 - Schulze, Patricia S. C. A1 - Bett, Alexander J. A1 - Bivour, Martin A1 - Caprioglio, Pietro A1 - Gerspacher, Fabian M. A1 - Kabaklı, Özde Ş. A1 - Richter, Armin A1 - Stolterfoht, Martin A1 - Zhang, Qinxin A1 - Neher, Dieter A1 - Hermle, Martin A1 - Hillebrecht, Harald A1 - Glunz, Stefan W. A1 - Goldschmidt, Jan Christoph T1 - 25.1% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber JF - Solar RRL N2 - Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future. KW - heterojunction silicon solar cells KW - interfaces KW - perovskite solar cells KW - tandem solar cells KW - thin films Y1 - 2020 VL - 4 IS - 7 PB - John Wiley & Sons, Inc. CY - New Jersey ER - TY - JOUR A1 - Raoufi, Meysam A1 - Hörmann, Ulrich A1 - Ligorio, Giovanni A1 - Hildebrandt, Jana A1 - Pätzel, Michael A1 - Schultz, Thorsten A1 - Perdigón-Toro, Lorena A1 - Koch, Norbert A1 - List-Kratochvil, Emil A1 - Hecht, Stefan A1 - Neher, Dieter T1 - Simultaneous effect of ultraviolet radiation and surface modification on the work function and hole injection properties of ZnO thin films JF - Physica Status Solidi. A , Applications and materials science N2 - The combined effect of ultraviolet (UV) light soaking and self-assembled monolayer deposition on the work function (WF) of thin ZnO layers and on the efficiency of hole injection into the prototypical conjugated polymer poly(3-hexylthiophen-2,5-diyl) (P3HT) is systematically investigated. It is shown that the WF and injection efficiency depend strongly on the history of UV light exposure. Proper treatment of the ZnO layer enables ohmic hole injection into P3HT, demonstrating ZnO as a potential anode material for organic optoelectronic devices. The results also suggest that valid conclusions on the energy-level alignment at the ZnO/organic interfaces may only be drawn if the illumination history is precisely known and controlled. This is inherently problematic when comparing electronic data from ultraviolet photoelectron spectroscopy (UPS) measurements carried out under different or ill-defined illumination conditions. KW - charge injection across hybrid interfaces KW - energy-level alignments KW - hybrid metal oxides KW - organic interfaces Y1 - 2020 U6 - https://doi.org/10.1002/pssa.201900876 SN - 1862-6300 SN - 1862-6319 VL - 217 IS - 5 SP - 1 EP - 6 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Wang, Qiong A1 - Smith, Joel A. A1 - Skroblin, Dieter A1 - Steele, Julian A. A1 - Wolff, Christian Michael A1 - Caprioglio, Pietro A1 - Stolterfoht, Martin A1 - Köbler, Hans A1 - Turren-Cruz, Silver-Hamill A1 - Li, Meng A1 - Gollwitzer, Christian A1 - Neher, Dieter A1 - Abate, Antonio T1 - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1210 KW - cesium lead halides KW - crystal orientation KW - inorganic perovskites KW - ISOS-L-1I protocol KW - phase purity KW - photostability Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525374 SN - 1866-8372 IS - 9 ER - TY - JOUR A1 - Chigarev, Vladimir A1 - Kazakov, Alexey A1 - Pikovsky, Arkady T1 - Kantorovich-Rubinstein-Wasserstein distance between overlapping attractor and repeller JF - Chaos : an interdisciplinary journal of nonlinear science N2 - We consider several examples of dynamical systems demonstrating overlapping attractor and repeller. These systems are constructed via introducing controllable dissipation to prototypic models with chaotic dynamics (Anosov cat map, Chirikov standard map, and incompressible three-dimensional flow of the ABC-type on a three-torus) and ergodic non-chaotic behavior (skew-shift map). We employ the Kantorovich-Rubinstein-Wasserstein distance to characterize the difference between the attractor and the repeller, in dependence on the dissipation level. Y1 - 2020 U6 - https://doi.org/10.1063/5.0007230 SN - 1054-1500 SN - 1089-7682 VL - 30 IS - 7 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Schaffenroth, Veronika A1 - Casewell, Sarah L. A1 - Schneider, D. A1 - Kilkenny, David A1 - Geier, Stephan A1 - Heber, Ulrich A1 - Irrgang, Andreas A1 - Przybilla, Norbert A1 - Marsh, Thomas R. A1 - Littlefair, Stuart P. A1 - Dhillon, Vik S. T1 - A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era JF - Monthly notices of the Royal Astronomical Society N2 - Subdwarf B stars are core-helium-burning stars located on the extreme horizontal branch (EHB). Extensive mass loss on the red giant branch is necessary to form them. It has been proposed that substellar companions could lead to the required mass loss when they are engulfed in the envelope of the red giant star. J08205+0008 was the first example of a hot subdwarf star with a close, substellar companion candidate to be found. Here, we perform an in-depth re-analysis of this important system with much higher quality data allowing additional analysis methods. From the higher resolution spectra obtained with ESO-VLT/XSHOOTER, we derive the chemical abundances of the hot subdwarf as well as its rotational velocity. Using the Gaia parallax and a fit to the spectral energy distribution in the secondary eclipse, tight constraints to the radius of the hot subdwarf are derived. From a long-term photometric campaign, we detected a significant period decrease of -3.2(8) x 10(-12) dd(-1). This can be explained by the non-synchronized hot subdwarf star being spun up by tidal interactions forcing it to become synchronized. From the rate of period decrease we could derive the synchronization time-scale to be 4 Myr, much smaller than the lifetime on EHB. By combining all different methods, we could constrain the hot subdwarf to a mass of 0.39-0.50 M-circle dot and a radius of R-sdB = 0.194 +/- 0.008 R-circle dot, and the companion to 0.061-0.071 M-circle dot with a radius of R-comp = 0.092 +/- 0.005 R-circle dot, below the hydrogen-burning limit. We therefore confirm that the companion is most likely a massive brown dwarf. KW - stars: abundances KW - stars: atmospheres KW - stars: fundamental parameters KW - stars: horizontal branch KW - stars: low-mass KW - subdwarfs Y1 - 2020 U6 - https://doi.org/10.1093/mnras/staa3661 SN - 0035-8711 SN - 1365-2966 VL - 501 IS - 3 SP - 3847 EP - 3870 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Pelisoli, Ingrid A1 - Vos, Joris A1 - Geier, Stephan A1 - Schaffenroth, Veronika A1 - Baran, Andrzej S. T1 - Alone but not lonely BT - observational evidence that binary interaction is always required to form hot subdwarf stars JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Hot subdwarfs are core-helium burning stars that show lower masses and higher temperatures than canonical horizontal branch stars. They are believed to be formed when a red giant suffers an extreme mass-loss episode. Binary interaction is suggested to be the main formation channel, but the high fraction of apparently single hot subdwarfs (up to 30%) has prompted single star formation scenarios to be proposed.Aims. We investigate the possibility that hot subdwarfs could form without interaction by studying wide binary systems. If single formation scenarios were possible, there should be hot subdwarfs in wide binaries that have undergone no interaction.Methods. Angular momentum accretion during interaction is predicted to cause the hot subdwarf companion to spin up to the critical velocity. The effect of this should still be observable given the timescales of the hot subdwarf phase. To study the rotation rates of companions, we have analysed light curves from the Transiting Exoplanet Survey Satellite for all known hot subdwarfs showing composite spectral energy distributions indicating the presence of a main sequence wide binary companion. If formation without interaction were possible, that would also imply the existence of hot subdwarfs in very wide binaries that are not predicted to interact. To identify such systems, we have searched for common proper motion companions with projected orbital distances of up to 0.1 pc to all known spectroscopically confirmed hot subdwarfs using Gaia DR2 astrometry.Results. We find that the companions in composite hot subdwarfs show short rotation periods when compared to field main sequence stars. They display a triangular-shaped distribution with a peak around 2.5 days, similar to what is observed for young open clusters. We also report a shortage of hot subdwarfs with candidate common proper motion companions. We identify only 16 candidates after probing 2938 hot subdwarfs with good astrometry. Out of those, at least six seem to be hierarchical triple systems, in which the hot subdwarf is part of an inner binary.Conclusions. The observed distribution of rotation rates for the companions in known wide hot subdwarf binaries provides evidence of previous interaction causing spin-up. Additionally, there is a shortage of hot subdwarfs in common proper motion pairs, considering the frequency of such systems among progenitors. These results suggest that binary interaction is always required for the formation of hot subdwarfs. KW - subdwarfs KW - binaries: general KW - stars: variables: general Y1 - 2020 U6 - https://doi.org/10.1051/0004-6361/202038473 SN - 0004-6361 SN - 1432-0746 VL - 642 PB - EDP Sciences CY - Les Ulis ER - TY - THES A1 - Jay, Raphael Martin T1 - Principles of charge distribution and separation BT - the case of iron complexes probed by X-ray spectroscopy N2 - The electronic charge distributions of transition metal complexes fundamentally determine their chemical reactivity. Experimental access to the local valence electronic structure is therefore crucial in order to determine how frontier orbitals are delocalized between different atomic sites and electronic charge is spread throughout the transition metal complex. To that end, X-ray spectroscopies are employed in this thesis to study a series of solution-phase iron complexes with respect to the response of their local electronic charge distributions to different external influences. Using resonant inelastic X-ray scattering (RIXS) and X-ray absorption spectroscopy (XAS) at the iron L-edge, changes in local charge densities are investigated at the iron center depending on different ligand cages as well as solvent environments. A varying degree of charge delocalization from the metal center onto the ligands is observed, which is governed by the capabilities of the ligands to accept charge density into their unoccupied orbitals. Specific solvents are furthermore shown to amplify this process. Solvent molecules of strong Lewis-acids withdraw charge from the ligand allowing in turn for more metal charge to be delocalized onto the ligand. The resulting local charge deficiencies at the metal center are, however, counteracted by competing electron-donation channels from the ligand towards the iron, which are additionally revealed. This is interpreted as a compensating effect which strives to maintain local charge densities at the iron center. This mechanism of charge density preservation is found to be of general nature. Using time-resolved RIXS and XAS at the iron L-edge, an analogous interplay of electron donation and back-donation channels is also revealed for the case of charge-transfer excited states. In such transient configurations, the electronic occupation of iron-centered frontier orbitals has been altered by an optical excitation. Changes in local charge densities that are expected to follow an increased or decreased population of iron-centered orbitals are, however, again counteracted. By scaling the degree of electron donation from the ligand onto the metal, local charge densities at the iron center can be efficiently maintained. Since charge-transfer excitations, however, often constitute the initial step in many electron transfer processes, these findings challenge common notions of charge-separation in transition metal dyes. KW - L-edge spectroscopy KW - charge-transfer excitations KW - transition metal complexes KW - electronic structure KW - photo-chemical pathways Y1 - 2020 ER - TY - JOUR A1 - Cabalar, Pedro A1 - Fandiño, Jorge A1 - Lierler, Yuliya T1 - Modular Answer Set Programming as a formal specification language JF - Theory and practice of logic programming N2 - In this paper, we study the problem of formal verification for Answer Set Programming (ASP), namely, obtaining aformal proofshowing that the answer sets of a given (non-ground) logic programPcorrectly correspond to the solutions to the problem encoded byP, regardless of the problem instance. To this aim, we use a formal specification language based on ASP modules, so that each module can be proved to capture some informal aspect of the problem in an isolated way. This specification language relies on a novel definition of (possibly nested, first order)program modulesthat may incorporate local hidden atoms at different levels. Then,verifyingthe logic programPamounts to prove some kind of equivalence betweenPand its modular specification. KW - Answer Set Programming KW - formal specification KW - formal verification KW - modular logic programs Y1 - 2020 U6 - https://doi.org/10.1017/S1471068420000265 SN - 1471-0684 SN - 1475-3081 VL - 20 IS - 5 SP - 767 EP - 782 PB - Cambridge University Press CY - New York ER - TY - THES A1 - Köhler, Raphael T1 - Towards seasonal prediction: stratosphere-troposphere coupling in the atmospheric model ICON-NWP N2 - Stratospheric variability is one of the main potential sources for sub-seasonal to seasonal predictability in mid-latitudes in winter. Stratospheric pathways play an important role for long-range teleconnections between tropical phenomena, such as the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO), and the mid-latitudes on the one hand, and linkages between Arctic climate change and the mid-latitudes on the other hand. In order to move forward in the field of extratropical seasonal predictions, it is essential that an atmospheric model is able to realistically simulate the stratospheric circulation and variability. The numerical weather prediction (NWP) configuration of the ICOsahedral Non-hydrostatic atmosphere model ICON is currently being used by the German Meteorological Service for the regular weather forecast, and is intended to produce seasonal predictions in future. This thesis represents the first extensive evaluation of Northern Hemisphere stratospheric winter circulation in ICON-NWP by analysing a large set of seasonal ensemble experiments. An ICON control climatology simulated with a default setup is able to reproduce the basic behaviour of the stratospheric polar vortex. However, stratospheric westerlies are significantly too weak and major stratospheric warmings too frequent, especially in January. The weak stratospheric polar vortex in ICON is furthermore connected to a mean sea level pressure (MSLP) bias pattern resembling the negative phase of the Arctic Oscillation (AO). Since a good representation of the drag exerted by gravity waves is crucial for a realistic simulation of the stratosphere, three sensitivity experiments with reduced gravity wave drag are performed. Both a reduction of the non-orographic and orographic gravity wave drag respectively, lead to a strengthening of the stratospheric vortex and thus a bias reduction in winter, in particular in January. However, the effect of the non-orographic gravity wave drag on the stratosphere is stronger. A third experiment, combining a reduced orographic and non-orographic drag, exhibits the largest stratospheric bias reductions. The analysis of stratosphere-troposphere coupling based on an index of the Northern Annular Mode demonstrates that ICON realistically represents downward coupling. This coupling is intensified and more realistic in experiments with a reduced gravity wave drag, in particular with reduced non-orographic drag. Tropospheric circulation is also affected by the reduced gravity wave drag, especially in January, when the strongly improved stratospheric circulation reduces biases in the MSLP patterns. Moreover, a retuning of the subgrid-scale orography parameterisations leads to a significant error reduction in the MSLP in all months. In conclusion, the combination of these adjusted parameterisations is recommended as a current optimal setup for seasonal simulations with ICON. Additionally, this thesis discusses further possible influences on the stratospheric polar vortex, including the influence of tropical phenomena, such as QBO and ENSO, as well as the influence of a rapidly warming Arctic. ICON does not simulate the quasi-oscillatory behaviour of the QBO and favours weak easterlies in the tropical stratosphere. A comparison with a reanalysis composite of the easterly QBO phase reveals, that the shift towards the easterly QBO in ICON further weakens the stratospheric polar vortex. On the other hand, the stratospheric reaction to ENSO events in ICON is realistic. ICON and the reanalysis exhibit a weakened stratospheric vortex in warm ENSO years. Furthermore, in particular in winter, warm ENSO events favour the negative phase of the Arctic Oscillation, whereas cold events favour the positive phase. The ICON simulations also suggest a significant effect of ENSO on the Atlantic-European sector in late winter. To investigate the influence of Arctic climate change on mid-latitude circulation changes, two differing approaches with transient and fixed sea ice conditions are chosen. Neither ICON approach exhibits the mid-latitude tropospheric negative Arctic Oscillation circulation response to amplified Arctic warming, as it is discussed on the basis of observational evidence. Nevertheless, adding a new model to the current and active discussion on Arctic-midlatitude linkages, further contributes to the understanding of divergent conclusions between model and observational studies. N2 - Die stratosphärische Variabilität ist eine der wichtigsten potentiellen Quellen für die Vorhersagbarkeit der atmosphärischen Zirkulation in den mittleren Breiten im Winter auf der Zeitskala von Wochen bis zu Jahreszeiten. Stratosphärische Prozesse spielen eine grundlegende Rolle für die Fernverbindungen (Telekonnektionen) zwischen tropischen Klimaphänomenen, wie der quasi-zweijährigen Schwingung (QBO) oder „El Niño-Südliche Oszillation“ (ENSO), und den mittleren Breiten, sowie den Telekonnektionen zwischen arktischen Klimaänderungen und der atmosphärischen Zirkulation in den mittleren Breiten. Die Fähigkeit eines atmosphärischen Modells, die stratosphärische Zirkulation und deren Variabilität realistisch zu simulieren, ist deshalb von grundlegender Bedeutung, um die Jahreszeitenvorhersage in den mittleren Breiten deutlich zu verbessern. Das nichthydrostatische Atmosphärenmodell ICON (ICOsahedral Non-hydrostatic atmosphere model) wird gegenwärtig beim Deutschen Wetterdienst (DWD) in der numerischen Wettervorhersagekonfiguration (ICON-NWP) für die Wettervorhersage genutzt, und soll zukünftig auch für Jahreszeitenvorhersagen benutzt werden. Darauf basierend, präsentiert die vorliegende Arbeit eine Vielzahl von saisonalen Ensembleexperimenten mit ICON-NWP und liefert damit die erste umfassende Bewertung der stratosphärischen Winterzirkulation der nördlichen Hemisphäre in ICON-NWP. Die Klimatologie eines ICON-Modelllaufs im Standardsetup reproduziert die grundlegenden Eigenschaften des stratosphärischen Polarwirbels. Allerdings sind die stratosphärischen Westwinde deutlich schwächer als in den Beobachtungen, und starke Stratosphärenerwärmungen treten insbesondere im Januar zu häufig auf. Zudem ist der schwache stratosphärische Polarwirbel in ICON mit einem typischen Fehler-Muster des Bodenluftdrucks verknüpft, welches der negativen Phase der Arktischen Oszillation (AO) ähnelt. Da eine gute Darstellung des von Schwerewellen ausgeübten Widerstands für eine realistische Simulation der Stratosphäre entscheidend ist, werden drei Sensitivitätsexperimente mit reduziertem Schwerewellenwiderstand durchgeführt. Sowohl eine Verringerung des nicht-orographischen, als auch eine Verringerung des orographischen Schwerewellenwiderstands führen jeweils zu einer Verstärkung des stratosphärischen Wirbels und damit zu einer Verringerung des Fehlers im Winter, insbesondere im Januar. Die Wirkung des nicht-orographischen Schwerewellenwiderstands auf die Stratosphäre ist hierbei jedoch stärker. Ein drittes Experiment, welches den reduzierten orographischen und nicht-orographischen Widerstand kombiniert, zeigt die größten Verbesserungen in der Stratosphäre. Die auf dem Index des „Northern Annular Mode“ basierende Analyse der Stratosphären-Troposphären-Kopplung zeigt, dass ICON die nach unten gerichtete Kopplung zwischen der Stratosphäre und Troposphäre realistisch darstellt. Diese Kopplung wird in Experimenten mit einem reduzierten Schwerewellenwiderstand verstärkt und realistischer dargestellt, dies gilt insbesondere für den reduzierten nicht-orographischen Widerstand. Auch die troposphärische Zirkulation wird durch den reduzierten Schwerewellenwiderstand beeinflusst, vor allem im Januar, wenn die stark verbesserte stratosphärische Zirkulation den Fehler in den Bodenluftdruckfeldern reduziert. Darüber hinaus führt ein Tuning der Parameterisierung der subgrid-skaligen orographischen Schwerewellen zu einer signifikanten Fehlerreduktion des Bodenluftdrucks in allen Monaten. Die Kombination all dieser angepassten Parametrisierungen wird als derzeit optimales Setup für Jahreszeiten-Simulationen mit ICON vorgeschlagen. Darüber hinaus werden in dieser Arbeit weitere mögliche Einflussfaktoren auf den stratosphärischen Polarwirbel diskutiert, darunter der Einfluss tropischer Phänomene, wie QBO und ENSO, sowie der Einfluss einer sich rasch erwärmenden Arktis. Das quasi-oszillierende Verhalten der QBO wird durch ICON nicht simuliert, sodass schwache Ostwinde in der tropischen Stratosphäre dominieren. Ein Vergleich mit einem Reanalyse-Komposit der östlichen QBO-Phase zeigt, dass die Verschiebung in Richtung der östlichen QBO in ICON den stratosphärischen Polarwirbel weiter abschwächt. Die stratosphärische Reaktion auf ENSO-Ereignisse in ICON ist jedoch realistisch. ICON und Reanalysedaten zeigen einen abgeschwächten Stratosphärenwirbel in warmen ENSO-Jahren. Darüber hinaus begünstigen insbesondere im Winter warme ENSO-Ereignisse die negative Phase der Arktischen Oszillation, während kalte Ereignisse die positive Phase begünstigen. Die ICON-Simulationen deuten auch auf einen signifikanten Effekt von ENSO auf den atlantisch-europäischen Sektor im Spätwinter hin. Um den Einfluss des arktischen Klimawandels auf Änderungen der Zirkulation in mittleren Breiten zu untersuchen, werden zwei unterschiedliche Ansätze mit transienten und festen Meereisgrenzen gewählt. Keiner der beiden ICON-Ansätze zeigt eine Tendenz zur negativen Phase der Arktische Oszillation als Reaktion auf die verstärkte Erwärmung der Arktis, wie sie in der Literatur anhand von Beobachtungsdaten häufig diskutiert wird. Jedoch wird somit der aktuellen und aktiven Diskussion zu den Auswirkungen des arktischen Klimawandels auf die Zirkulation der mittleren Breiten ein neues Modell hinzugefügt. T2 - Im Hinblick auf die Jahreszeitenvorhersage: Stratosphären-Troposphären-Kopplung in dem Atmosphärenmodell ICON-NWP KW - Seasonal prediction KW - Stratosphere-troposphere coupling KW - ICON KW - Stratospheric polar vortex KW - Jahreszeitenvorhersage KW - Stratosphären-Troposphären-Kopplung KW - ICON KW - Stratosphärischer Polarwirbel KW - El Niño-Southern Oscillation (ENSO) KW - El Niño-Südliche Oszillation KW - Arctic-midlatitude linkages KW - Verbindungspfade zwischen der Arktis und den mittleren Breiten Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-487231 ER - TY - JOUR A1 - Abdalla, H. A1 - Adam, R. A1 - Aharonian, Felix A. A1 - Benkhali, F. Ait A1 - Angüner, Ekrem Oǧuzhan A1 - Arcaro, C. A1 - Armand, C. A1 - Armstrong, T. A1 - Ashkar, H. A1 - Backes, M. A1 - Baghmanyan, V. A1 - Martins, V. Barbosa A1 - Barnacka, A. A1 - Barnard, M. A1 - Becherini, Y. A1 - Berge, D. A1 - Bernlohr, K. A1 - Bi, B. A1 - Bottcher, M. A1 - Boisson, C. A1 - Bolmont, J. A1 - de Lavergne, M. de Bony A1 - Bordas, Pol A1 - Breuhaus, M. A1 - Brun, F. A1 - Brun, P. A1 - Bryan, M. A1 - Buchele, M. A1 - Bulik, T. A1 - Bylund, T. A1 - Caroff, S. A1 - Carosi, A. A1 - Casanova, Sabrina A1 - Chand, T. A1 - Chandra, S. A1 - Chen, A. A1 - Cotter, G. A1 - Curylo, M. A1 - Mbarubucyeye, J. Damascene A1 - Davids, I. D. A1 - Davies, J. A1 - Deil, C. A1 - Devin, J. A1 - deWilt, P. A1 - Dirson, L. A1 - Djannati-Atai, A. A1 - Dmytriiev, A. A1 - Donath, A. A1 - Doroshenko, V. A1 - Duffy, C. A1 - Dyks, J. A1 - Egberts, Kathrin A1 - Eichhorn, F. A1 - Einecke, S. A1 - Emery, G. A1 - Ernenwein, J. -P. A1 - Feijen, K. A1 - Fegan, S. A1 - Fiasson, A. A1 - de Clairfontaine, G. Fichet A1 - Fontaine, G. A1 - Funk, S. A1 - Fussling, Matthias A1 - Gabici, S. A1 - Gallant, Y. A. A1 - Giavitto, G. A1 - Giunti, L. A1 - Glawion, D. A1 - Glicenstein, J. F. A1 - Gottschall, D. A1 - Grondin, M. -H. A1 - Hahn, J. A1 - Haupt, M. A1 - Hermann, G. A1 - Hinton, J. A. A1 - Hofmann, W. A1 - Hoischen, Clemens A1 - Holch, T. L. A1 - Holler, M. A1 - Horbe, M. A1 - Horns, D. A1 - Huber, D. A1 - Jamrozy, M. A1 - Jankowsky, D. A1 - Jankowsky, F. A1 - Jardin-Blicq, A. A1 - Joshi, V. A1 - Jung-Richardt, I. A1 - Kasai, E. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Khangulyan, D. A1 - Khelifi, B. A1 - Klepser, S. A1 - Kluzniak, W. A1 - Komin, Nu. A1 - Konno, R. A1 - Kosack, K. A1 - Kostunin, D. A1 - Kreter, M. A1 - Lamanna, G. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Levy, C. A1 - Lohse, T. A1 - Lypova, I. A1 - Mackey, J. A1 - Majumdar, J. A1 - Malyshev, D. A1 - Malyshev, D. A1 - Marandon, V. A1 - Marchegiani, P. A1 - Marcowith, Alexandre A1 - Mares, A. A1 - Marti-Devesa, G. A1 - Marx, R. A1 - Maurin, G. A1 - Meintjes, P. J. A1 - Meyer, M. A1 - Mitchell, A. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mohrmann, L. A1 - Montanari, A. A1 - Moore, C. A1 - Morris, P. A1 - Moulin, Emmanuel A1 - Muller, J. A1 - Murach, T. A1 - Nakashima, K. A1 - Nayerhoda, A. A1 - de Naurois, M. A1 - Ndiyavala, H. A1 - Niederwanger, F. A1 - Niemiec, J. A1 - Oakes, L. A1 - O'Brien, Patrick A1 - Odaka, H. A1 - Ohm, S. A1 - Olivera-Nieto, L. A1 - Wilhelmi, E. de Ona A1 - Ostrowski, M. A1 - Oya, I. A1 - Panter, M. A1 - Panny, S. A1 - Parsons, R. D. A1 - Peron, G. A1 - Peyaud, B. A1 - Piel, Q. A1 - Pita, S. A1 - Poireau, V. A1 - Noel, A. Priyana A1 - Prokhorov, D. A. A1 - Prokoph, H. A1 - Puhlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Rauth, R. A1 - Reichherzer, P. A1 - Reimer, A. A1 - Reimer, O. A1 - Remy, Q. A1 - Renaud, M. A1 - Rieger, F. A1 - Rinchiuso, L. A1 - Romoli, C. A1 - Rowell, G. A1 - Rudak, B. A1 - Ruiz-Velasco, E. A1 - Sahakian, V. A1 - Sailer, S. A1 - Sanchez, D. A. A1 - Santangelo, Andrea A1 - Sasaki, M. A1 - Scalici, M. A1 - Schussler, F. A1 - Schutte, H. M. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Seglar-Arroyo, M. A1 - Senniappan, M. A1 - Seyffert, A. S. A1 - Shafi, N. A1 - Shiningayamwe, K. A1 - Simoni, R. A1 - Sinha, A. A1 - Sol, H. A1 - Specovius, A. A1 - Spencer, S. A1 - Spir-Jacob, M. A1 - Stawarz, L. A1 - Sun, L. A1 - Steenkamp, R. A1 - Stegmann, C. A1 - Steinmassl, S. A1 - Steppa, C. A1 - Takahashi, T. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tiziani, D. A1 - Tluczykont, M. A1 - Tomankova, L. A1 - Trichard, C. A1 - Tsirou, M. A1 - Tuffs, R. A1 - Uchiyama, Y. A1 - van der Walt, D. J. A1 - van Eldik, C. A1 - van Rensburg, C. A1 - van Soelen, B. A1 - Vasileiadis, G. A1 - Veh, J. A1 - Venter, C. A1 - Vincent, P. A1 - Vink, J. A1 - Volk, H. J. A1 - Vuillaume, T. A1 - Wadiasingh, Z. A1 - Wagner, S. J. A1 - Watson, J. A1 - Werner, F. A1 - White, R. A1 - Wierzcholska, A. A1 - Wong, Yu Wun A1 - Yusafzai, A. A1 - Zacharias, M. A1 - Zanin, R. A1 - Zargaryan, D. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zhu, S. J. A1 - Ziegler, A. A1 - Zorn, J. A1 - Zouari, S. A1 - Zywucka, N. T1 - An extreme particle accelerator in the Galactic plane BT - HESS J1826-130 JF - Astronomy and astrophysics : an international weekly journal N2 - The unidentified very-high-energy (VHE; E > 0.1 TeV) gamma -ray source, HESS J1826-130, was discovered with the High Energy Stereoscopic System (HESS) in the Galactic plane. The analysis of 215 h of HESS data has revealed a steady gamma -ray flux from HESS J1826-130, which appears extended with a half-width of 0.21 degrees +/- 0.02
(stat)degrees
stat degrees +/- 0.05
(sys)degrees sys degrees . The source spectrum is best fit with either a power-law function with a spectral index Gamma = 1.78 +/- 0.10(stat) +/- 0.20(sys) and an exponential cut-off at 15.2
(+5.5)(-3.2) -3.2+5.5 TeV, or a broken power-law with Gamma (1) = 1.96 +/- 0.06(stat) +/- 0.20(sys), Gamma (2) = 3.59 +/- 0.69(stat) +/- 0.20(sys) for energies below and above E-br = 11.2 +/- 2.7 TeV, respectively. The VHE flux from HESS J1826-130 is contaminated by the extended emission of the bright, nearby pulsar wind nebula, HESS J1825-137, particularly at the low end of the energy spectrum. Leptonic scenarios for the origin of HESS J1826-130 VHE emission related to PSR J1826-1256 are confronted by our spectral and morphological analysis. In a hadronic framework, taking into account the properties of dense gas regions surrounding HESS J1826-130, the source spectrum would imply an astrophysical object capable of accelerating the parent particle population up to greater than or similar to 200 TeV. Our results are also discussed in a multiwavelength context, accounting for both the presence of nearby supernova remnants, molecular clouds, and counterparts detected in radio, X-rays, and TeV energies. KW - ISM: supernova remnants KW - ISM: clouds KW - gamma rays: general KW - gamma rays: KW - ISM Y1 - 2020 U6 - https://doi.org/10.1051/0004-6361/202038851 SN - 0004-6361 SN - 1432-0746 VL - 644 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Cheng, Xin A1 - Zhang, Jie A1 - Kliem, Bernhard A1 - Török, Tibor A1 - Xing, Chen A1 - Zhou, Zhenjun A1 - Inhester, Bernd A1 - Ding, Mingde T1 - Initiation and early kinematic evolution of solar eruptions JF - The Astrophysical Journal N2 - We investigate the initiation and early evolution of 12 solar eruptions, including six active-region hot channel and six quiescent filament eruptions, which were well observed by the Solar Dynamics Observatory, as well as by the Solar Terrestrial Relations Observatory for the latter. The sample includes one failed eruption and 11 coronal mass ejections, with velocities ranging from 493 to 2140 km s(-1). A detailed analysis of the eruption kinematics yields the following main results. (1) The early evolution of all events consists of a slow-rise phase followed by a main-acceleration phase, the height-time profiles of which differ markedly and can be best fit, respectively, by a linear and an exponential function. This indicates that different physical processes dominate in these phases, which is at variance with models that involve a single process. (2) The kinematic evolution of the eruptions tends to be synchronized with the flare light curve in both phases. The synchronization is often but not always close. A delayed onset of the impulsive flare phase is found in the majority of the filament eruptions (five out of six). This delay and its trend to be larger for slower eruptions favor ideal MHD instability models. (3) The average decay index at the onset heights of the main acceleration is close to the threshold of the torus instability for both groups of events (although, it is based on a tentative coronal field model for the hot channels), suggesting that this instability initiates and possibly drives the main acceleration. KW - solar coronal mass ejections KW - stellar coronal mass ejections KW - solar storm Y1 - 2020 U6 - https://doi.org/10.3847/1538-4357/ab886a SN - 1055-6796 SN - 1476-3540 VL - 894 IS - 2 SP - 1 EP - 20 PB - Cambridge Scientific Publishers CY - Cambridge ER - TY - JOUR A1 - Cervantes Villa, Juan Sebastian A1 - Shprits, Yuri Y. A1 - Aseev, Nikita A1 - Allison, Hayley J. T1 - Quantifying the effects of EMIC wave scattering and magnetopause shadowing in the outer electron radiation belt by means of data assimilation JF - Journal of geophysical research : Space physics N2 - In this study we investigate two distinct loss mechanisms responsible for the rapid dropouts of radiation belt electrons by assimilating data from Van Allen Probes A and B and Geostationary Operational Environmental Satellites (GOES) 13 and 15 into a 3-D diffusion model. In particular, we examine the respective contribution of electromagnetic ion cyclotron (EMIC) wave scattering and magnetopause shadowing for values of the first adiabatic invariant mu ranging from 300 to 3,000 MeV G(-1). We inspect the innovation vector and perform a statistical analysis to quantitatively assess the effect of both processes as a function of various geomagnetic indices, solar wind parameters, and radial distance from the Earth. Our results are in agreement with previous studies that demonstrated the energy dependence of these two mechanisms. We show that EMIC wave scattering tends to dominate loss at lower L shells, and it may amount to between 10%/hr and 30%/hr of the maximum value of phase space density (PSD) over all L shells for fixed first and second adiabatic invariants. On the other hand, magnetopause shadowing is found to deplete electrons across all energies, mostly at higher L shells, resulting in loss from 50%/hr to 70%/hr of the maximum PSD. Nevertheless, during times of enhanced geomagnetic activity, both processes can operate beyond such location and encompass the entire outer radiation belt. Y1 - 2020 U6 - https://doi.org/10.1029/2020JA028208 SN - 2169-9380 SN - 2169-9402 VL - 125 IS - 8 PB - American Geophysical Union CY - Washington ER - TY - GEN A1 - Ciemer, Catrin A1 - Rehm, Lars A1 - Kurths, Jürgen A1 - Donner, Reik Volker A1 - Winkelmann, Ricarda A1 - Boers, Niklas T1 - An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1207 KW - complex networks KW - droughts KW - prediction KW - Amazon rainforest Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525863 SN - 1866-8372 IS - 9 ER - TY - JOUR A1 - Ciemer, Catrin A1 - Rehm, Lars A1 - Kurths, Jürgen A1 - Donner, Reik Volker A1 - Winkelmann, Ricarda A1 - Boers, Niklas T1 - An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures JF - Environmental Research Letters N2 - Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months. KW - complex networks KW - droughts KW - prediction KW - Amazon rainforest Y1 - 2019 VL - 15 IS - 9 PB - IOP - Institute of Physics Publishing CY - Bristol ER - TY - JOUR A1 - Seroussi, Helene A1 - Nowicki, Sophie A1 - Payne, Antony J. A1 - Goelzer, Heiko A1 - Lipscomb, William H. A1 - Abe-Ouchi, Ayako A1 - Agosta, Cecile A1 - Albrecht, Torsten A1 - Asay-Davis, Xylar A1 - Barthel, Alice A1 - Calov, Reinhard A1 - Cullather, Richard A1 - Dumas, Christophe A1 - Galton-Fenzi, Benjamin K. A1 - Gladstone, Rupert A1 - Golledge, Nicholas R. A1 - Gregory, Jonathan M. A1 - Greve, Ralf A1 - Hattermann, Tore A1 - Hoffman, Matthew J. A1 - Humbert, Angelika A1 - Huybrechts, Philippe A1 - Jourdain, Nicolas C. A1 - Kleiner, Thomas A1 - Larour, Eric A1 - Leguy, Gunter R. A1 - Lowry, Daniel P. A1 - Little, Chistopher M. A1 - Morlighem, Mathieu A1 - Pattyn, Frank A1 - Pelle, Tyler A1 - Price, Stephen F. A1 - Quiquet, Aurelien A1 - Reese, Ronja A1 - Schlegel, Nicole-Jeanne A1 - Shepherd, Andrew A1 - Simon, Erika A1 - Smith, Robin S. A1 - Straneo, Fiammetta A1 - Sun, Sainan A1 - Trusel, Luke D. A1 - Van Breedam, Jonas A1 - van de Wal, Roderik S. W. A1 - Winkelmann, Ricarda A1 - Zhao, Chen A1 - Zhang, Tong A1 - Zwinger, Thomas T1 - ISMIP6 Antarctica BT - a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and assess the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimates of the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes, forcings employed and initial states of ice sheet models. This study presents results from ice flow model simulations from 13 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100 as part of the Ice Sheet Model Intercomparison for CMIP6 (ISMIP6). They are forced with outputs from a subset of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), representative of the spread in climate model results. Simulations of the Antarctic ice sheet contribution to sea level rise in response to increased warming during this period varies between 7:8 and 30.0 cm of sea level equivalent (SLE) under Representative Concentration Pathway (RCP) 8.5 scenario forcing. These numbers are relative to a control experiment with constant climate conditions and should therefore be added to the mass loss contribution under climate conditions similar to present-day conditions over the same period. The simulated evolution of the West Antarctic ice sheet varies widely among models, with an overall mass loss, up to 18.0 cm SLE, in response to changes in oceanic conditions. East Antarctica mass change varies between 6 :1 and 8.3 cm SLE in the simulations, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional simulated mass loss of 28mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the climate forcing, the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 climate models show an additional mass loss of 0 and 3 cm of SLE on average compared to simulations done under present-day conditions for the two CMIP5 forcings used and display limited mass gain in East Antarctica. Y1 - 2020 U6 - https://doi.org/10.5194/tc-14-3033-2020 SN - 1994-0416 SN - 1994-0424 VL - 14 IS - 9 SP - 3033 EP - 3070 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Reese, Ronja A1 - Levermann, Anders A1 - Albrecht, Torsten A1 - Seroussi, Helene A1 - Winkelmann, Ricarda T1 - The role of history and strength of the oceanic forcing in sea level projections from Antarctica with the Parallel Ice Sheet Model JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Mass loss from the Antarctic Ice Sheet constitutes the largest uncertainty in projections of future sea level rise. Ocean-driven melting underneath the floating ice shelves and subsequent acceleration of the inland ice streams are the major reasons for currently observed mass loss from Antarctica and are expected to become more important in the future. Here we show that for projections of future mass loss from the Antarctic Ice Sheet, it is essential (1) to better constrain the sensitivity of sub-shelf melt rates to ocean warming and (2) to include the historic trajectory of the ice sheet. In particular, we find that while the ice sheet response in simulations using the Parallel Ice Sheet Model is comparable to the median response of models in three Antarctic Ice Sheet Intercomparison projects - initMIP, LARMIP-2 and ISMIP6 - conducted with a range of ice sheet models, the projected 21st century sea level contribution differs significantly depending on these two factors. For the highest emission scenario RCP8.5, this leads to projected ice loss ranging from 1:4 to 4:0 cm of sea level equivalent in simulations in which ISMIP6 ocean forcing drives the PICO ocean box model where parameter tuning leads to a comparably low sub-shelf melt sensitivity and in which no surface forcing is applied. This is opposed to a likely range of 9:1 to 35:8 cm using the exact same initial setup, but emulated from the LARMIP-2 experiments with a higher melt sensitivity, even though both projects use forcing from climate models and melt rates are calibrated with previous oceanographic studies. Furthermore, using two initial states, one with a previous historic simulation from 1850 to 2014 and one starting from a steady state, we show that while differences between the ice sheet configurations in 2015 seem marginal at first sight, the historic simulation increases the susceptibility of the ice sheet to ocean warming, thereby increasing mass loss from 2015 to 2100 by 5% to 50 %. Hindcasting past ice sheet changes with numerical models would thus provide valuable tools to better constrain projections. Our results emphasize that the uncertainty that arises from the forcing is of the same order of magnitude as the ice dynamic response for future sea level projections. Y1 - 2020 U6 - https://doi.org/10.5194/tc-14-3097-2020 SN - 1994-0416 SN - 1994-0424 VL - 14 IS - 9 SP - 3097 EP - 3110 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Zeitz, Maria A1 - Levermann, Anders A1 - Winkelmann, Ricarda T1 - Sensitivity of ice loss to uncertainty in flow law parameters in an idealized one-dimensional geometry JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - Acceleration of the flow of ice drives mass losses in both the Antarctic and the Greenland Ice Sheet. The projections of possible future sea-level rise rely on numerical ice-sheet models, which solve the physics of ice flow, melt, and calving. While major advancements have been made by the ice-sheet modeling community in addressing several of the related uncertainties, the flow law, which is at the center of most process-based ice-sheet models, is not in the focus of the current scientific debate. However, recent studies show that the flow law parameters are highly uncertain and might be different from the widely accepted standard values. Here, we use an idealized flow-line setup to investigate how these uncertainties in the flow law translate into uncertainties in flow-driven mass loss. In order to disentangle the effect of future warming on the ice flow from other effects, we perform a suite of experiments with the Parallel Ice Sheet Model (PISM), deliberately excluding changes in the surface mass balance. We find that changes in the flow parameters within the observed range can lead up to a doubling of the flow-driven mass loss within the first centuries of warming, compared to standard parameters. The spread of ice loss due to the uncertainty in flow parameters is on the same order of magnitude as the increase in mass loss due to surface warming. While this study focuses on an idealized flow-line geometry, it is likely that this uncertainty carries over to realistic three-dimensional simulations of Greenland and Antarctica. Y1 - 2020 U6 - https://doi.org/10.5194/tc-14-3537-2020 SN - 1994-0416 SN - 1994-0424 VL - 14 IS - 10 SP - 3537 EP - 3550 PB - Copernicus CY - Göttingen ER -