The Deepwater Horizon (DwH) was not only the largest oil spill along the US coast, but perhaps also the most important oceanographic event over the past several decades. Numerical modeling and prediction of pollutant transport require a good understanding of the nature of multi-scale processes in the upper ocean. The Consortium for Advanced Research of Transport of Hydrocarbons in the Environment (CARTHE, carthe.org) have conducted the largest simultaneous drifter sampling attempted in oceanography to date in order to find out the scale-dependent dispersion characteristics near the DwH site. Upper ocean boundary layer simulations obtained with Nek5000 have been used to estimate the numbers and durations of drifter trajectories needed for this oceanic experiment. A total of 317 drifters, an order of magnitude larger than typical, have been deployed during so-called Grand Lagrangian Deployment (GLAD). The primary finding of GLAD is that dispersion depends on local processes in the region, in contrast
with results from operational ocean models that indicate the dominance of various large eddies. Several other oceanic applications of Nek5000 will also be discussed.