Visual analysis of uncertainties in ocean forecasts for planning and operation of off-shore structures

We present a novel integrated visualization system that enables interactive visual analysis of ensemble simulations used in ocean forecasting, i.e, simulations of sea surface elevation. Our system enables the interactive planning of both the placement and operation of off-shore structures. We illustrate this using a real-world simulation of the Gulf of Mexico. Off-shore structures, such as those used for oil exploration, are vulnerable to hazards caused by strong loop currents. The oil and gas industry therefore relies on accurate ocean forecasting systems for planning their operations. Nowadays, these forecasts are based on multiple spatio-temporal simulations resulting in multidimensional, multivariate and multivalued data, so-called ensemble data. Changes in sea surface elevation are a good indicator for the movement of loop current eddies, and our visualization approach enables their interactive exploration and analysis. We enable analysis of the spatial domain, for planning the placement of structures, as well as detailed exploration of the temporal evolution at any chosen position, for the prediction of critical ocean states that require the shutdown of rig operations.

1 Introduction

Oil exploration in the deep Gulf of Mexico is vulnerable to hazards due to strong currents at the fronts of highly nonlinear warm-core eddies [38]. The dynamics in the Gulf of Mexico are indeed dominated by the powerful northward Yucatan Current flowing into a semi-enclosed basin. This current forms a loop, called the Loop Current, that exits through the Florida Straits, and in turn merges with the Gulf Stream. At irregular intervals, the loop current sheds large eddies that propagate westward across the Gulf of Mexico. This eddy shedding involves a rapid growth of nonlinear instabilities [3], and the occasional eddy detachment and reattachment make it very difficult to clearly define, identify, monitor, and forecast an eddy shedding event [2], [4], [11]. Figure 1: A selected time step of an ocean forecasting ensemble computed for the Gulf of Mexico is visualized via the mean surface of the ensemble (center). for a more detailed inspection of the entire distribution of the surfaces comprising the ensemble, we provide two linked views. the first linked view (left) shows a histogram of depth positions of the surfaces at a selected spatial position and time step. The second linked view (right) is a time-series view that depicts a glyph for each time step at the selected position. the horizontal line corresponds to a chosen critical sea level, where each glyph's color depicts the risk corresponding to how much of the distribution is above that critical level