The feedback between plate tectonics and mantle convection controls the Earth's thermal evolution via the seafloor age distribution. We therefore designed the MACMA model to simulate time‐dependent plate tectonics in a 2D cylindrical geometry with evolutive plate boundaries, based on multiagent systems that express thermal and mechanical interactions. We compute plate velocities using a local force balance and use explicit parameterizations to treat tectonic processes such as trench migration, subduction initiation, continental breakup and plate suturing. These implementations allow the model to update its geometry and thermal state at all times. Our approach has two goals: (1) to test how empirically‐ and analytically‐determined rules for surface processes affect mantle and plate dynamics, and (2) to investigate how plate tectonics impact the thermal regime. Our predictions for driving forces, plate velocities and heat flux are in agreement with independent observations. Two time scales arise for the evolution of the heat flux: a linear long‐term decrease and high‐amplitude short‐term fluctuations due to surface tectonics. We also obtain a plausible thermal history, with mantle temperature decreasing by less than 200 K over the last 3 Gyr. In addition, we show that on the long term, mantle viscosity is less thermally influential than tectonic processes such as continental breakup or subduction initiation, because Earth's cooling rate depends mainly on its ability to replace old insulating seafloor by young thin oceanic lithosphere. We infer that simple convective considerations alone cannot account for the nature of mantle heat loss and that tectonic processes dictate the thermal evolution of the Earth.
Abstract In June 2012, Technip signed an agreement with Cervval (a specialist software company in Brittany) and Bureau Veritas (BV) to develop an ice-modelling simulation program. The long term aim is for the simulator to predict the flow of ice around both fixed and floating structures and calculate the ice-loadings on the platforms. The program will ultimately allow platform structures to be optimised, to minimise ice loadings and ice rubble build-up, prior to final design verification in an ice test basin. Initially the program has been developed to predict ice behaviour in shallow waters since there are several projects imminent in the North Caspian but will be equally applicable in Arctic regions. Cervval has been developing the software with ice expertise input and verification from BV. The program is unique in the Arctic industry in that it uses a multi-model simulator which is able to cope with the complexity of calculating the kinematic and failure behaviour for the ice sheet and for each ice fragment that results from contact with the structure or from collision with other ice rubble particles for ice mechanical properties. Currently the program is able to simulate the flow of an ice sheet as it encroaches on a conical structure, which is a type of platform design that Technip has developed specifically for projects offshore Kazakhstan. The design tool is able to predict vertical and horizontal loads on the structure with good accuracy. It also predicts the geometry of the ice accumulation in front of the structure above and below the ice sheet. The next stage in the software development is to consider ice interaction with a straight sloping wall structure, then vertical walled structures (such as artificial islands) and finally a range of floating structures. The paper presents details of the simulator, the status of the development & verification program and plans for the future. A typical set of ice simulations are shown and a comparison with ice basin test results is presented as a measure of the program's accuracy.
Abstract In June 2012, Technip signed an agreement with Cervval (a specialist software company in Brittany) and Bureau Veritas (BV) to develop an ice-modelling simulation program. The long term aim was for the simulator to predict the flow of ice around both fixed and floating structures and calculate the ice-loadings on the platforms. The program would allow platform structures to be optimised, to minimise ice loadings and ice rubble build-up, prior to final design verification in an ice test basin. Initially the program was developed to predict ice behaviour in shallow waters since there are several projects imminent in the North Caspian but would be equally applicable in Arctic regions. Cervval has developed the software with ice expertise input and verification from BV. The program is unique in the Artic industry in that it uses a multi-model simulator which is able to cope with the complexity of calculating the kinematic and failure behaviour for the ice sheet and for each newly created ice fragment that results from contact with the structure or due to collision with other ice rubble particles for ice mechanical properties. At ATC 2014 , the program was first presented to the industry but was still under development. At that stage, the program was able to simulate the flow of an ice sheet as it encroached on a conical structure and to predict vertical and horizontal loads on the structure with good accuracy. It also predicted the geometry of the ice accumulation in front of the structure above and below the ice sheet. Since ATC 2014, the software development has considered ice interaction with straight sloping wall structures, then vertical walled structures (such as artificial islands) and finally a range of floating structures. This follow-up paper will present details of the completed simulator, the verification program and plans for the future. A typical set of ice simulations will be shown and a comparison with ice basin test results will be presented as a measure of the program's accuracy.
Abstract Exploitation of the Arctic's resources requires the mastery of the risks caused by extreme ice conditions. The design of offshore structures subjected to extreme ice conditions is a challenge for engineers since there are very few advanced design tools available on the market, especially those able to cope with the large variety of ice interaction and failure mechanisms. Different approaches have been used to model and study ice behavior. Among them are analytical, numerical and empirical approaches with different models being considered. Each model has its own advantages and drawbacks and is only generally dedicated to certain circumstances. In 2012 Technip, Cervval and Bureau Veritas initiated a common development program to offer a new tool for the design of offshore structures interacting with ice (Septseault, 2014, 2015) combining a variety of approaches and models. After three years, the first version of the Ice-MAS software (www.ice-mas.com) is now available. It simulates the ice loadings on a structure and the dynamic behavior of the drifting ice-sheet and floes around. Thanks to multi-agent technology, it is possible to combine in a common framework multiple phenomena from various natures and heterogeneous scales (drag, friction, ice-sheet bending failure, local crushing, rubble stack up) (Le Yaouanq, 2015). This work has been the subject of numerous validations, particularly by comparison with ice basin and in-situ results (Dudal, 2015). The Ice-MAS development program continues in 2016 with the addition of a capability to model the interaction of icebergs with offshore structures. This paper will introduce the co-simulation architecture proposed to simulate the complex interaction between an iceberg and a platform structure. It will focus on the hydrodynamic behavior of the platform and the iceberg including its stability. It will also consider the interaction between both bodies; including the non-linearity of the mooring system (in the case of a floating platform) and the local fracture mechanisms of the iceberg. The objective is to propose a new more accurate design method that will improve the overall ice management system for a project.
