Drift and deformation of oil slicks due to surface waves

Abstract

We present a theoretical model for the wave-induced drift and horizontal deformation of an oil slick. The waves and the mean flow are coupled through the influence of the mean flow on the concentration of slick material, which in turn determines the damping rate of the waves and hence the transfer of momentum from the waves to the mean flow. We also briefly discuss a simplified version of the model that can be used when remote sensing data are available. With this simpler model the wave-induced forcing of the mean flow is obtained directly from observations of the wave field, hence knowledge of any specific slick properties is not required.

Measurement and modeling of oil slick transport

“…In fact, the presence of the oil slicks may enhance such a shear, as the oil‐water interfacial gradient may suppress the turbulence and subsequent transfer of stress into the ocean. This process depends on the slick rheology, and nonlinear interactions between the slick and surface waves in the capillary‐gravity range may lead to a rapid redistribution of slick material, leading to rapid changes in the surface wave damping rates [ Christensen and Terrile , ]. The isolated effect of this process on the larger spatial and temporal scales considered here is not well known, and cannot easily be distinguished from the overall effect of other turbulent processes (e.g., Langmuir turbulence), making the problem very complicated.…”

“…Waves enhance vertical mixing of surface oil, with the actual depth of downward mixing and its possible return to the surface dependent on wave height, turbulence, and wind, along with the oil droplet size, mass, and resultant buoyancy. Christensen and Terrile [] assessed the role of waves on oil drift, the damping of waves within the slick based on the properties of the oil, and the impact on the transfer of energy from the waves to the mean flow. The Stokes drift, the net velocity in the direction of wave propagation of a particle moving within the flow of a wave, is an additional component of the transport.…”

Drift in the uppermost part of the ocean

“…Objects in the upper few meters are exposed to the wave-induced Stokes drift [Stokes, 1847;Monismith and Fong, 2004;Röhrs et al, 2014]. In addition, dissipation of wave momentum [e.g., Carniel et al, 2009;Christensen and Terrile, 2009] and the interaction of wave momentum with planetary vorticity (the so-called Coriolis-Stokes force [Ursell, 1950;Hasselmann, 1970]) alter the underlying Eulerian currents. For example, Lewis and Belcher [2004] show that the Coriolis-Stokes force deflects the surface current by about 10 ∘ -20 ∘ farther to the right (Northern Hemisphere) compared to the classic steady Ekman balance (see also Polton et al [2005]).…”

Synergistic surface current mapping by spaceborne stereo imaging and coastal HF radar

“…Furthermore, for these calm conditions we have assumed that the slicks undergo relatively little deformation over the (45.3 s) time interval separating the paired images. A detailed comparison of slick shapes in both the forward and nadir views sometimes reveals a pixel‐scale “smudging” of features particularly in the later (nadir) image, which may reflect shape evolution due to dynamical effects [e.g., Weber , 2001; Christensen and Terrile , 2009] and/or the effects of the changing view geometry. The view‐angle dependence is of particular importance with regard to inter‐image comparability and in other situations may lead to the “brightness reversal” phenomenon [ Matthews et al , 2004; Matthews , 2005; Matthews et al , 2008].…”