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Can floating plastic pollution be observed by satellites through wave damping?



Prime contractor
Organisational Unit
Implementation progress
25 November 2021

Duration: 13 months


Dark bands associated with wave damping can be observed in SAR images of  the ocean surface. In some cases, the dampening is associated with algal blooms or oil slicks. However, there are some images where the cause of these dark bands is not clear, as is the case of the attached SAR image taken of the Atlantic Ocean (acquired on 10th June  2014 by Sentinel-1, credits: ESA). The accumulation of floating marine  pollution, particularly plastic, has been suggested as a candidate mechanism. There is no convincing scientific evidence to either confirm or rule out this hypothesis. The proposed co-funded research will  examine whether it is theoretically possible for floating marine litter to significantly affect the properties of surface  waves, so that its signature can be detected by satellites, a question existing models cannot answer. The direct  analogue of the possible influence of floating plastic pollution upon waves is  sea ice, which is well-known to dampen surface waves, changing their amplitude and wavelength, thus enabling their observation by satellites [1,2]. However, the size of plastic particles is generally smaller and more sparsely distributed than floating ice. In unsteady flows, particles with a low Stokes number (non-dimensional size) are advected perfectly by the flow, whereas the inertia of larger particles with a high Stokes number determines their motion. These high-Stokes-number particles can also  potentially dampen the motion of the fluid, as there will be a velocity  difference between the particles and the fluid and, consequently, a drag  force that dissipates energy. Larger particles and a larger concentration increase the dissipation rate. The co-funded research project will develop the first theoretical model (based  on [3]) to estimate the minimum concentrations and floating plastic pollution characteristics needed to significantly affect the surface wave field, in turn allowing detection by satellites, using SAR in particular.

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Can floating plastic pollution be observed by satellites through wave damping?