The OceanParcels team goes to the Wadden Sea
How do plastic items move through the Wadden Sea? To answer that question, the OceanParcels team led by Erik van Sebille at IMAU went on two expeditions to the north of the Netherlands, to deploy 24 so-called Stokes drifters made possible by a crowd-funding campaign by the Utrecht University Fund. These Stokes drifters are frisbee-shaped gps-tracked devices that communicate their location via Iridium satellite and are specifically designed to chart ocean surface currents.
The first expedition was on 14 November 2023, onboard the R/V Adriaen Coenen that sailed from the NIOZ harbor on Texel. With twelve team members and a journalist, we set out to deploy drifters in three batches of nine, nine and six drifters each, to map out the flow in the western part of the Dutch Wadden Sea.
The flow patterns were much more complex than anticipated, see this map for an interactive animation. Most of the drifters ended up on beaches and the Afsluitdijk multiple times, and because they had stickers with contact information, many were returned after being found. Thus, we could redeploy 12 of the drifters for a second time, this time in the eastern part of the Dutch Wadden Sea.
Because there was no ship available, we deployed them from the mud flats. With the help of Jelle Soons, we walked a kilometre or so out onto the Wad near Moddergat at low tide on 25 April 2024, and left the drifters on the mud there.
As the tide came in, the drifters started to move. First southwards towards the dike, but soon they veered westward and then northward, and within a matter of hours they had all left the Wadden Sea. Ever since, they have been roaming the North Sea, where they can be tracked live on this map.
We’re now analysing the drifter trajectories, comparing them against different ocean flow products from Rijkswaterstaat and the EU’s Copernicus Marine Service. The ultimate goal of the project is to develop better numerical models to forecast how plastic items move through the unique Wadden Sea.
For more information, see the project webpage.
