Fishing on Europe: Dynamics of the Jovian moon and its subsurface ocean

The interior of Europa, one of the moons in the Jovian system, is still mainly unknown. There are, however, indications that below an icy outer layer a subsurface ocean is present. Moreover, it has been estimated that in total the ice and ocean are between 80 and 170 kilometers thick. Concerning the thickness of the ice layer, there exist two hypotheses: some believe this layer is relatively thin (up to approximately ten kilometers), whereas others think the ice layer will be much thicker. Since it is expected that the global deformation rate of Europa, caused by the gravity pull of Jupiter, gives insight in the interior of this moon, it is of great interest to investigate this by means of computational models. The main question to be answered in this thesis is: how does the subsurface ocean of Europa deform, due to the tidal pull of Jupiter? To answer this question, the tidal forcing by Jupiter is determined. This tidal potential can be subdivided in a constant tidal potential and a time varying part. Only the latter results in an exchange in tidal energy and time-varying deformation and is, therefore, of interest. The global deformation of Europa due to this time-varying forcing is studied by means of the normal mode analysis. For this analysis, it is assumed that Europa consists of four coupled homogeneous layers; the core, the mantle, the ocean and the sea ice layer. From the normal mode analysis it followed that the radial deformation of Europa in the absence of an ocean, is less than one meter, whereas this deformation is approximately 20 meters if an ocean is present. From these results it can be concluded that by measuring the actual global deformation, for instance by means of future satellite measurements, the presence of an ocean can be determined. The next step is to model the ocean by means of the MIT General Circulation Model (MITgcm), a model that was originally developed for Earth. In this model, the ocean is no longer assumed to be homogeneous. Without sea ice, an ocean of 100 kilometers deep radially deforms approximately 20 meters due to the time-varying tidal potential. In case of an ocean with a depth of 100 kilometers and a sea ice layer with a thickness of ten kilometers, the Europan surface still radially deforms approximately 20 meters, from which it follows that the sea ice layer does not reduce the ocean deformation, i.e. the sea ice acts fluidly. This was also obtained from the normal mode analysis. Furthermore, it follows that the tidal forcing disturbs the geostrophic balance in the ocean and that the ocean dynamics, due to the tidal forcing are driven by the vertical velocities. Since the mantle is also subject to tidal deformation, heat will also be generated in this layer. On Io, for instance, volcanoes are present and it is therefore reasonable to assume that volcanoes are also present on the ocean floor of Europa. These volcanoes release the tidal heat from the mantle in the ocean. Consequently, the sea ice experiences extra heating, which leads to additional melting. This may be a strong argument for the thin sea ice hypothesis. In addition, it is shown that the shallower the ocean, the higher the ocean velocities. Thus, the presence of subsurface volcanoes and, for example, ridges will locally result in higher ocean velocities. It may well be the case that these disturbances in the velocity field and the heat released by volcanoes result in melt troughs and produce the characteristic cracks visible on the Europan surface.Aerospace Engineerin

Flooding of tunnels: quantifying climate change effects on infrastructure

To develop climate proof road infrastructure it is of importance to understand the quantitative effects of expected climate change on the performance of individual components, such as tunnels and road sections, and their contributions to the performance of the overall road network.A full understanding of quantitative effects on infrastructure and the effect of measures is currently lacking. In this study, a method is developed to quantify the effects of climate change on infrastructure by performing a resilience analysis of individual objects. To illustrate this method the frequency of flooding due to (extreme) rainfall induced by climate change of a fictitious tunnel in The Netherlands, is studied as a test case. This structured method is a promising technique that might be a good basis for decision making processes. The analysis shows that several data is missing, both climatological data as well as quantified requirements on the performance of infrastructural components

Message Dissemination in Social Networks for Support of Information Operations Planning

Message dissemination is often an important part of many provincial reconstruction efforts. This dissemination is affected by many factors that may only be partly known, such as the impact of the information, the social network structure, socio-cultural factors that affect the information dissemination, and at what point the information looses its news value in verbal communication. Understanding and managing how all factors that affect the message dissemination may interact pose a complex problem even for experienced Psychological Operations (PsyOps) officers. This paper therefore proposes that modelling and simulation (MoS) techniques based on epidemiological modelling can be used to cope with the complexity when planning information operations. Particularly, regarding what portion of the target population is reached by a message and within what timeframe. The paper describes how the epidemiological framework can be applied to a scenario that is used for combined staff exercises within the Swedish Armed Forces. The main focus is how cross-cultural dimensions, such as Hofstede's five dimensions, and other socio-cultural factors can be used to derive the social network structure and contact rate for message dissemination. The results illustrate the assumed effects of socio-cultural factors on message dissemination and the need for a coherent theoretical framework that provides some understanding of how the social network and contact rates are shaped by socio-cultural factors