Erik van Sebille

We study floating marine macro plastic pollution with a dedicated campaign where we released and tracked 24 shallow surface drifters in the Dutch Wadden Sea, an intertidal region where water dynamics are driven by semi-diurnal tides and wind. The campaign captured water surface transport patterns, and around 150 observations of the drifters interacting with the coast and mudflats, where groundings of varying durations occurred. We identify these transitions in the recorded trajectories from manual inspection, and formulate and evaluate a statistical approach for the automatic detection of grounded drifters. We then characterize the transitions by relating them to the coinciding wind conditions and tides, and with the duration of the groundings. The results of this analysis generally agree with the intuitions that wind towards the coast increases the frequency of interactions and that the drifters are rarely re-floated during falling tides. Furthermore, we find that groundings tend to be shorter duration when they occur shorter before the next high tide. We present multiple visualizations that characterize the groundings in more detail. The results provide a statistical characterization of coastal interactions that can be integrated in models and used for the planning of beach-cleanups. They may be improved by considering the specific environmental conditions of the campaign, and by analyzing the influence of the weight and size of the drifters, which are both larger than typical floating macroplastic.

The climate crisis is an existential threat to modern society. Climate researchers are in an important position, with their academic knowledge of climate, to engage with the issue of climate change through advocacy. It has been explored how climate researchers in academia navigate their engagement, but not how climate researchers affiliated with governmental institutes do so. Considering their unique position in the science and policymaking nexus, we conducted 14 interviews with researchers at different Dutch government-funded knowledge organizations that support policy-making with (scientific) knowledge to understand how they engage with climate change. Separating the responses into fundamental epistemological and ontological arguments for and against advocacy, we find that climate researchers at these government-funded knowledge organizations see opportunities for advocacy, but also see concerns. While some of these concerns are similar to those working in academia (including the dissonant tone of the action, pressure from managers and colleagues, and lack of time), we also find concerns unique to working at a government-funded knowledge organization – such as their role as civil servants including their independence and impartiality, the mismatch with the institutional identity, and unclear rules about what is allowed. We suggest that researchers at government-funded knowledge organizations delineate their roles and responsibilities within society more clearly, following a value-based approach.

The Atlantic Meridional Overturning Current (AMOC) may be approaching a tipping point, with potentially significant environmental and societal consequences. Here, we examine the framing and accuracy of Dutch news articles reporting on the AMOC slowdown or potential collapse using peer-reviewed scientific research papers. In total, we analysed 17 scientific papers and 73 news articles published between 1999 and 2025 using qualitative coding, and eight scientists were interviewed to assess their opinion on the representation of their research in these news articles. Our analysis reveals that Dutch news articles often omit methodological detail and scientific uncertainties, while emphasizing the timing of an AMOC collapse. Dutch news articles simplify terminology, use types of exaggeration, and localize information to engage a broader public. Although most interviewed scientists consider the media coverage of their research adequate, they identify areas for improvement and propose solutions. Overall, Dutch journalistic media often accurately convey the core concepts of AMOC-related scientific research papers, but place strong emphasis on societal consequences and opportunities of an AMOC collapse.

The climate crisis is an existential threat to modern society. Climate researchers are in an important position, with their academic knowledge of climate, to engage with the issue of climate change through advocacy and/or activism. It has been explored how climate researchers in academia navigate their engagement, but not how climate researchers affiliated with governmental institutes do so. Considering their unique position in the science and policymaking nexus, we conducted 14 interviews with researchers at different Dutch government-funded knowledge organizations that support policy-making with (scientific) knowledge to understand how they engage with climate change. Separating the responses into fundamental epistemological and ontological arguments for and against advocacy, we find that climate researchers at these government-funded knowledge organizations see opportunities for advocacy and activism, but also see concerns. While some of these concerns are similar to those working in academia (including on the dissonant tone of the action, pressure from managers and colleagues, and lack of time), we also find concerns unique to working at a government-funded knowledge organization – such as their role as civil servants including their independence and impartiality, the mismatch with the institutional identity, and unclear rules about what is allowed. We suggest that researchers at government-funded knowledge organizations delineate their roles and responsibilities within society more clearly, following a value-based approach.

The climate crisis is an existential threat to modern society. Climate researchers are in an important position, with their academic knowledge of climate, to engage with the issue of climate change through advocacy and/or activism. It has been explored how climate researchers in academia navigate their engagement, but not how climate researchers affiliated with governmental institutes do so. Considering their unique position in the science and policymaking nexus, we conducted 14 interviews with researchers at different Dutch government-funded knowledge organizations that support policy-making with (scientific) knowledge to understand how they engage with climate change. Separating the responses into fundamental epistemological and ontological arguments for and against advocacy, we find that climate researchers at these government-funded knowledge organizations see opportunities for advocacy and activism, but also see concerns. While some of these concerns are similar to those working in academia (including on the dissonant tone of the action, pressure from managers and colleagues, and lack of time), we also find concerns unique to working at a government-funded knowledge organization – such as their role as civil servants including their independence and impartiality, the mismatch with the institutional identity, and unclear rules about what is allowed. We suggest that researchers at government-funded knowledge organizations delineate their roles and responsibilities within society more clearly, following a value-based approach.

Blooms of the seaweed Sargassum have been reported in the Tropical Atlantic Ocean and Caribbean Sea since 2011. Large-scale inundation events of this seaweed in coastal regions have a negative impact on both the economy and the environment. To predict the timing, location and quantity of Sargassum strandings, model frameworks that link open ocean distributions to coastal regions are required. Here, we develop an open-source customizable Lagrangian simulation framework and growth model for Sargassum that combines transport by currents, wind and waves with a biological modelling framework that includes dynamic growth limitation depending on temperature, nitrate availability and salinity. The framework can use satellite detections of the Sargassum Watch System (SaWS) to initialise virtual Sargassum particles in the Tropical Atlantic Ocean. We demonstrate that the combination of physical transport and biological growth strongly affects Sargassum distribution, with substantial variability on spatio-temporal scales. We show that temperature is the strongest growth-limiting parameter, and in particular that elevated surface temperatures, together with low salinity from the Amazon River plume, play a crucial role in Sargassum decline.

Blooms of the seaweed Sargassum have been reported in the Tropical Atlantic Ocean and Caribbean Sea since 2011. Large-scale inundation events of this seaweed in coastal regions have a negative impact on both the economy and the environment. To predict the timing, location and quantity of Sargassum strandings, model frameworks that link open ocean distributions to coastal regions are required. Here, we develop an open-source customizable Lagrangian simulation framework and growth model for Sargassum that combines transport by currents, wind and waves with a biological modelling framework that includes dynamic growth limitation depending on temperature, nitrate availability and salinity. The framework can use satellite detections of the Sargassum Watch System (SaWS) to initialise virtual Sargassum particles in the Tropical Atlantic Ocean. We demonstrate that the combination of physical transport and biological growth strongly affects Sargassum distribution, with substantial variability on spatio-temporal scales. We show that temperature is the strongest growth-limiting parameter, and in particular that elevated surface temperatures, together with low salinity from the Amazon River plume, play a crucial role in Sargassum decline.

Blooms of the seaweed Sargassum have been reported in the Tropical Atlantic Ocean and Caribbean Sea since 2011. Large-scale inundation events of this seaweed in coastal regions have a negative impact on both the economy and the environment. To predict the timing, location and quantity of Sargassum strandings, model frameworks that link open ocean distributions to coastal regions are required. Here, we develop an open-source customizable Lagrangian simulation framework and growth model for Sargassum that combines transport by currents, wind and waves with a biological modelling framework that includes dynamic growth limitation depending on temperature, nitrate availability and salinity. The framework can use satellite detections of the Sargassum Watch System (SaWS) to initialise virtual Sargassum particles in the Tropical Atlantic Ocean. We demonstrate that the combination of physical transport and biological growth strongly affects Sargassum distribution, with substantial variability on spatio-temporal scales. We show that temperature is the strongest growth-limiting parameter, and in particular that elevated surface temperatures, together with low salinity from the Amazon River plume, play a crucial role in Sargassum decline.

The climate crisis is an existential threat to modern society. Climate researchers are in an important position, with their academic knowledge of climate, to engage with the issue of climate change through advocacy and/or activism. It has been explored how climate researchers in academia navigate their engagement, but not how climate researchers affiliated with governmental institutes do so. Considering their unique position in the science and policymaking nexus, we conducted 14 interviews with researchers at different Dutch government-funded knowledge organizations that support policy-making with (scientific) knowledge to understand how they engage with climate change. Separating the responses into fundamental epistemological and ontological arguments for and against advocacy, we find that climate researchers at these government-funded knowledge organizations see opportunities for advocacy and activism, but also see concerns. While some of these concerns are similar to those working in academia (including on the dissonant tone of the action, pressure from managers and colleagues, and lack of time), we also find concerns unique to working at a government-funded knowledge organization – such as their role as civil servants including their independence and impartiality, the mismatch with the institutional identity, and unclear rules about what is allowed. We suggest that researchers at government-funded knowledge organizations delineate their roles and responsibilities within society more clearly, following a value-based approach.

The climate crisis is an existential threat to modern society. Climate researchers are in an important position, with their academic knowledge of climate, to engage with the issue of climate change through advocacy and/or activism. It has been explored how climate researchers in academia navigate their engagement, but not how climate researchers affiliated with governmental institutes do so. Considering their unique position in the science and policymaking nexus, we conducted 14 interviews with researchers at different Dutch government-funded knowledge organizations that support policy-making with (scientific) knowledge to understand how they engage with climate change. Separating the responses into fundamental epistemological and ontological arguments for and against advocacy, we find that climate researchers at these government-funded knowledge organizations see opportunities for advocacy and activism, but also see concerns. While some of these concerns are similar to those working in academia (including on the dissonant tone of the action, pressure from managers and colleagues, and lack of time), we also find concerns unique to working at a government-funded knowledge organization – such as their role as civil servants including their independence and impartiality, the mismatch with the institutional identity, and unclear rules about what is allowed. We suggest that researchers at government-funded knowledge organizations delineate their roles and responsibilities within society more clearly, following a value-based approach.