Effects of chemical dispersants on oil spill drift paths in the German Bight—probabilistic assessment based on numerical ensemble simulations

Abstract

Oil dispersed in the water column remains sheltered from wind forcing, so that an altered drift path is a key consequence of using chemical dispersants. In this study, ensemble simulations were conducted based on 7 years of simulated atmospheric and marine conditions, evaluating 2,190 hypothetical spills from each of 636 cells of a regular grid covering the inner German Bight (SE North Sea). Each simulation compares two idealized setups assuming either undispersed or fully dispersed oil. Differences are summarized in a spatial map of probabilities that chemical dispersant applications would help prevent oil pollution from entering intertidal coastal areas of the Wadden Sea. High probabilities of success overlap strongly with coastal regions between 10 m and 20 m water depth, where the use of chemical dispersants for oil spill response is a particularly contentious topic. The present study prepares the ground for a more detailed net environmental benefit analysis (NEBA) accounting also for toxic effects.

Monitoring concepts for an evaluation of marine environmental states in the German Bight

“…Using a Lagrangian tracer modelling system, the origin and fate of water masses and pollutants in the complex flows of coastal and shelf seas can be reconstructed. Schwichtenberg et al (2016a) used this modelling approach in ensemble simulations of a probabilistic assessment of oil spills. The effects of chemical dispersants on oil spill drift paths in the German Bight were evaluated and shown in probability maps.…”