Lagrangian studies in the Western Mediterranean Sea

Abstract

[eng] The Mediterranean Sea is one of the most significant seas in the history of humanity. Its biodiversity and natural resources have made it one of the cornerstones in the development of the countries surrounding it. However, nowadays, there is an ongoing deterioration of coastal waters, not only in this sea but also in many of our oceans, thus harming marine life in many parts of the world. For this reason, action plans such as the Sustainable Development Goals (SDGs 2030) were developed. This agenda seeks to initiate efforts, through the collaboration of businesses, scientific communities, and institutions, to address these issues, including the preservation of marine life and the oceans. Based on this, many institutions have been working to meet these objectives, using innovative tools and providing new perspectives on this problem, including the application of Lagrangian tools to ocean studies. The Lagrangian perspective has been widely used in fields such as oceanography because it allows tracking the movement of particles and determining their trajectories based on the velocity field. These particles can range from fluid particles, nutrients and to marine organisms, which can help understand ocean circulation, track certain marine species, and monitor the diffusion of pollutants. Nowadays, there is a significant increase in water contamination. It is believed that nearly five million metric tonnes of plastic enter the oceans annually. Considering these facts and the new tools at our disposal, groups of people are making new conservation and environmental campaigns to achieve better results. In a study conducted by Baudena et al. [1], it was found that one of the major pathways for a significant quantity of microplastics in the Mediterranean Sea is located in the north of Mallorca. This point is of great interest as it allows us to focus efforts in this area and conduct cleanup campaigns to collect a higher quantity of microplastics with fewer resources. This information can also provide insights into the primary sources of microplastics that pass through this point. In this study, we made certain approximations to simulate the behavior of plastic particles in the ocean. One of them was we consider that these are floating particles, therefore, these do not sink, thus allowing us to make the trajectory of the particle on the surface of the ocean. We integrated backward trajectories during two different seasons of the year, winter and summer, to identify the regions from which microplastic particles passing through the north of Mallorca originate. We conducted this analysis during two different seasons to determine if there were any seasonal variations. In the end, we found that there was a change in origin regions between the two seasons. In summer, over 60% of the microplastics came from the Alboran Sea and Algeria, while in winter, nearly 50% originated from the Ligurian Sea and the Gulf of Lyon. With these percentages and knowing when they predominate during the year, we can focus on cleanup campaigns and develop laws to protect the Mediterranean Sea and its marine life.