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During my PhD, I was applying the clumped isotope technique to modern brachiopods and fossil belemnites, and I conducted methodological work. Carbonate clumped isotope thermometry is a tool to reconstruct carbonate precipitation temperatures. In contrast to oxygen isotope thermometry, i.e., the δ18O-thermometer, the carbonate clumped isotope thermometer does not require an estimate for the oxygen isotope composition of the seawater, as it considers the fractionation of isotopes exclusively amongst carbonate isotopologues. The ∆47 value of a carbonate expresses the abundance of the 13C–18O bond bearing carbonate isotopologue, within the carbonate, relative to its random distribution. In thermodynamic equilibrium, the ∆47 value of a given carbonate is solely a function of the carbonate precipitation temperature. However, kinetic isotope fractionations, i.e., vital effects, driven by diffusion, pH or incomplete oxygen isotope exchange between water and dissolved inorganic carbonate species can cause the carbonate to be precipitated with isotopic compositions that are offset from those predicted for thermodynamic equilibrium.
Brachiopods serve as important geochemical archives of past climate conditions. To investigate the nature and significance of kinetic controls on brachiopod shell δ18O and ∆47 values, in collaboration with the BASE-LiNE Earth ITN, I analysed the bulk and clumped isotope compositions of eighteen modern brachiopod shells, collected from different geographic locations and water depths that cover a substantial range of growth temperatures. Growth temperatures and seawater δ18O values for each brachiopod were independently determined. Most of the analysed brachiopods exhibit combined offsets from clumped and oxygen isotope equilibrium, and there is a significant negative correlation between the offset values. The observed correlation slope between offset ∆47 and offset δ18O point to the importance of kinetic effects associated with Knudsen diffusion and incomplete hydration and hydroxylation of CO2 (aq), occurring during biomineralisation. The correlations between the growth rates of the analysed brachiopods and both the offset ∆47 and the offset δ18O values provide further arguments for the presence of kinetic effects. In conclusion, the oxygen and clumped isotope composition of modern brachiopod shells are affected by growth rate-induced kinetic effects that hinder their use for palaeoceanography.
There seems to be a wide agreement in critical geographic thought that Hegel is dead, as to end up with Hegel’s idealism serves to be the starting point for the materialist project of critical geographies. This paper aims to call this starting point into question by confronting Henri Lefebvre with Slavoj Žižek. While Lefebvre, one of the pioneers of materialist geographic thought, intensively worked on a metaphilosophical critique to open Hegel’s testament, Žižek’s Hegel supposed to pave the way for a new philosophical materialism. This paper seeks to claim that such a materialist Hegel not only survives the critical encounter of Lefebvre’s metaphilosophy, but also encourages us to inquire about the possibilities and consequences of a geographical turn to Hegel. What if there is a Hegel out there that geography has not even detected?
Air-sea feedbacks between the Mediterranean Sea and the atmosphere on various temporal and spatial scales play a major role in the Mediterranean regional climate system and beyond. The Mediterranean Sea is a source of moisture due to excess evaporation and, on a long-term average, is associated with a warming of the lower atmosphere in contact with the sea surface due to heat loss at the air-sea interface. The complex air-sea interactions and feedbacks in the Mediterranean basin strongly modulate the sea surface fluxes and favor several cyclogenetic activities under certain meteorological conditions. Examples of such cyclonic activities are medicanes (Mediterranean hurricanes) and Vb-cyclones. Medicanes are mesoscale, marine, and warm-core Mediterranean cyclones that exhibit some similarities to tropical cyclones, while Vb-cyclones are extra-tropical cyclones, that propagate from the Western Mediterranean Sea and travel across the Eastern European Alps into the Central European region. Extremely strong winds and heavy precipitation associated with these cyclones can lead to severe destruction and flooding. Changes in the intensity and frequency of these cyclones are also projected under changing future climate conditions, where the Mediterranean region has been identified as a hotspot in terms of rising temperatures.
The development of high-resolution regional climate models (RCMs) has progressed our understanding of the processes characterizing the Mediterranean climate. However, large uncertainties still exist regarding the estimates of air-sea fluxes, which, in turn, affect the simulation of the Mediterranean climate. Several factors can be attributed to such discrepancies, such as data quality, temporal and spatial resolution, and the misrepresentation of physical processes. To overcome some of these inconsistencies and deficiencies of the existing climate simulations, a new high-resolution atmosphere-ocean regional coupled model (AORCM) has been developed to simulate the air-sea feedback mechanisms. This coupled model incorporates the coupling of RCM COSMO-CLM (CCLM) and the regional ocean model NEMO-MED12 for the Mediterranean Sea (MED) as well as NEMO-NORDIC for the North- and Baltic Sea (NORDIC). Several experiments were performed using both the coupled and uncoupled models to investigate the impact of air-sea interactions and feedbacks on sea surface heat fluxes, wind speed, and on the formation of Mediterranean cyclones (i.e., medicanes and Vb-cyclones). These experiments were performed using different horizontal atmospheric grid resolutions to analyze the effect of resolution on sea surface heat fluxes, wind speed, and the development of medicanes.
The results of the present study indicate that a finer atmospheric grid resolution ([is as appreciated as]9 vs. [is as appreciated as]50 km) improved the wind speed simulations (particularly near coastal areas) and subsequently improved the simulations of the turbulent heat fluxes. Both parameters were better simulated in the coupled simulations than in the uncoupled simulations, but coupling introduced a warm SST bias in winter. Radiation fluxes were slightly better represented in coarse-grid simulations than in fine-grid simulations. However, the higher-resolution coupled model could reproduce the observed net outgoing total surface heat flux over the Mediterranean Sea. In addition to that sub diurnal SST variations have a strong effect on sub-daily heat fluxes and wind speed but minor effects at longer timescales. Regarding the impact of atmospheric grid resolution ([is as appreciated as]50, 25, and [is as appreciated as]9 km) and ocean coupling on medicanes, it was detected that the coupled model with a finer atmospheric grid ([is as appreciated as]9 km) was able to not only reproduce most medicane events, but also improved the track length, warm core, and wind speed compared to the uncoupled model. The coupled model with the coarse-grid ([is as appreciated as]50 and [is as appreciated as]25 km) did not show any improvement in simulating medicanes compared to the uncoupled model. The spectral nudging technique, applied on the wind components above 850 hPa in the interior domain to keep large-scale circulation close to the driving data (i.e., ERAInterim reanalysis), improved the accuracy of the times and locations of generated medicanes, but no improvement was found in the track length and intensity.
Concerning the role of the Mediterranean Sea coupling on Vb cyclones, the investigation showed that atmosphere-ocean coupling had an overall positive impact, although with a strong case-by-case variation, on the trajectories and intensity of Vb-cyclones as a result of the variation in moisture source for each event. In general, all model configurations could replicate Vbcyclones, their trajectories, and associated precipitation fields. The average structure of the precipitation field was best represented in the coupled simulations. Coupling of the North- and Baltic Seas also showed an improvement in some of the simulated Vb-cyclones.
The atmosphere-ocean coupling showed an overall positive impact on the simulation of sea surface heat fluxes and Mediterranean cyclones (medicanes and Vb-cyclones). Moreover, the representation of sea surface heat fluxes, wind speed, and medicane features was more realistic when using a finer atmospheric grid resolution (less than 10 km). The present study suggests that the combination of a finer atmospheric grid resolution together with atmosphere-ocean coupling is advantageous in simulating the Mediterranean climate system.
Im Rahmen einer angewandten kritischen Geographie beschäftigen wir uns in unserer Masterarbeit mit Realen Utopien auf Quartiersebene und zeigen, dass eine alternative Neuausrichtung der Stadtplanung und -entwicklung nötig und möglich ist. Die Grundlage dafür bildet eine kritische Auseinandersetzung mit dem Begriff der Utopie und der Ebene des Quartiers. Das städtische Quartier bildet einen Möglichkeitsraum, einen space of hope (Harvey 2000), in dem Alternativen jenseits kapitalistischer Verwertungsinteressen praktiziert und gelebt werden können. Diesen Möglichkeitsraum gilt es vielfältig zu gestalten und gegenwärtigen, neoliberalen Stadtentwicklungs-paradigmen Reale Utopien(Wright 2017a) entgegenzustellen. Dabei stellt sich die Frage: Welche Gegenentwürfe zu aktuell herrschenden Paradigmen in der Stadtentwicklung zeigen uns Wege aus der Alternativlosigkeit und hin zu einer solidarischen Praxis auf Quartiersebene?Für die Beantwortung dieser Frage werden potentielle und bereits existierende Reale Utopien identifiziertund analysiert. In dieser Analyse werden Instrumente, Forderungen und Strategien herausgearbeitet, derer es Bedarf um Risse im kapitalistischem System auszuweiten, zu verteidigen und zu verstetigen. Die Ergebnisse lassen sich unter den Begriffen der Solidarität, Dekommodifi-zierung, Demokratisierung und Vergesellschaftung zusammenfassen. Sie sind die zentralen Bedin-gungen, die für die Verwirklichung Realer Utopien und damit für gesellschaftliche Transformation, entscheidend sind. Darauf basierendwird ein Kompass für ein solidarisches Quartier erarbeitet.
In many parts of the world, the centralized grid provides energy to the population only to a limited extent. The electrification for sub-Saharan Africa countries is the lowest in the world, representing half of the world's population withoutelectricity. However, during the last years there has been an increased attention to rural areas in the Global South beyond the centralised grid, especially with respect to improved possibilities of solar power systems. The transition from one dominant form of energy provision to various alternatives includes different dimensions and depends on specific socio-spatial contexts. Energy systems are framed within systems of spatial practices, performed by a variety of involved actors, like consumers, local suppliers, international for-profit companies, international development donors as well as national and regional authorities. As such power systems arealways cause and effect of socio-technical change This study takes the example of Rwanda to analyse the marketization of decentralised energy systems. Based on empirical field work with energy entrepreneurs it combines Post-Colonial Theory with Science and Technology-Studies to theorise the role of energy to the social production of space beyond the grid.
There is a broad consensus that psychoanalytic theory cannot offer an account to further engage with the ontological turn toward the object that human sciences face today. In particular, the structuralist side of psychoanalysis, most prominently promoted by Jacques Lacan, is supposed to be unable to grasp an object independently from the subject. Against this background, it is no surprise that ‘object-oriented’ geographers ignore psychoanalytic theory. My aim is to investigate the interstices between the object-oriented turn and Lacanian psychoanalysis. I argue that the critiques miss a crucial aspect of Lacan’s ontology: he does not question that there are objects located ‘out there’, but rather adds that psychoanalysis engages with another object whose location remains uncertain. I follow Lacan’s most important invention, the object a, to argue that this object is crucial to understanding the ontology of Lacan as an ‘object-disoriented’ ontology. While object-oriented approaches in cultural geography give ontological priority to the material conditions of existence, Lacanian ontology allows us to understand how material objects become spectralized through an immaterial surplus. To substantiate this claim, I explore the role of anxiety with regard to the Sathorn Unique Tower, an abandoned skyscraper sitting in the middle of Bangkok. Widely known as the ‘Ghost Tower’, this ruin is internationally considered to be haunted. By focusing on a movie and an interview about the Ghost Tower as well as my own ethnographic observation of it, I not only explore the topological dimension of the ghost but also demonstrate that it is precisely the impossibility of localization that enables an object to disorientate the subject.