Coastal current convergence structures in the Bay of Biscay from optimized high-frequency radar and satellite data.

The southeastern Bay of Biscay has been described as a "dead end" for floating marine litter, often accumulating along small-scale linear streaks. Coastal Current Convergence Structures (CCS), often associated with vertical motions at river plume edges, estuarine fronts, or other physical processes, can be at the origin of the accumulation. Understanding the formation of CCS and their role in the transport of marine litter is essential to better quantify and to help mitigate marine litter pollution. The Lagrangian framework, used to estimate the absolute dispersion, and the finite-size Lyapunov exponents (FSLE), have proved very effective for identifying CCS in the current velocity field. However, the quality of CCS identification depends strongly on the Eulerian fields. Two surface current velocity data sets were used in the analysis: the remotely sensed velocities from the EuskOOS High-Frequency Radar (HFR) network and velocities from three-dimensional model outputs. They were complemented by drifting buoy velocity measurements. An optimization method, involving the fusion of drifting buoys and HFR velocities is proposed to better reconstruct the fine-scale structure of the current velocity field. Merging these two sources of velocity data reduced the mean Lagrangian error and the Root Mean Square Error (RMSE) by 50 % and 30 % respectively, significantly improving velocity reconstruction. FSLE ridgelines obtained from the Lagrangian analysis of optimized velocities were compared with remotely sensed concentrations of Chlorophyll-a. It was shown that ridgelines control the spatial distribution of phytoplankton. They fundamentally represent the CCS which can potentially affect marine litter aggregation. Analysis of the absolute dispersion revealed large stirring in the alongshore direction which was also confirmed by spatial distribution of FSLE ridgelines. The alignment between FSLE ridgelines and patterns of high Chlorophyll-a concentration was observed, often determining the limits of river plume expansion in the study area.

Developing bottom drifters to better understand the stranding locations of cold-stunned sea turtles in Cape Cod Bay, Massachusetts.

Every fall, juvenile sea turtles in the Northwest Atlantic Ocean are threatened by rapidly declining water temperatures. When sea turtles become hypothermic, or cold-stunned, they lose mobility-either at the surface, subsurface, or the bottom of the water column-and eventually strand at the shoreline where rescue teams associated with the Sea Turtle Stranding and Salvage Network may search for them. Understanding the effects of ocean currents on the potential stranding locations of cold-stunned sea turtles is essential to better understand stranding hotspots and increase the probability of successful discovery and recovery of turtles before they die in the cold temperatures. Traditional oceanographic drifters-instruments used to track currents-have been used to examine relationships between current and stranding locations in Cape Cod Bay, but these drifters are not representative of sea turtle morphology and do not assess how bottom currents affect stranding locations. To address these knowledge gaps, we designed new drifters that represent the shape and dimensions of sea turtles-one that can float at the surface and one that sinks to the bottom-to track both surface and bottom currents in Cape Cod Bay. We found a marked difference between the trajectories of our new drifter models and those that were previously used for similar research. These findings bring us one step closer to identifying the transport pathways for cold-stunned sea turtles and optimizing cold-stunned sea turtle search and rescue efforts in Cape Cod.

The Smart Drifter Cluster: Monitoring Sea Currents and Marine Litter Transport Using Consumer IoT Technologies.

The study of marine Lagrangian transport holds significant importance from a scientific perspective as well as for practical applications such as environmental-pollution responses and prevention (e.g., oil spills, dispersion/accumulation of plastic debris, etc.). In this regard, this concept paper introduces the Smart Drifter Cluster: an innovative approach that leverages modern "consumer" IoT technologies and notions. This approach enables the remote acquisition of information on Lagrangian transport and important ocean variables, similar to standard drifters. However, it offers potential benefits such as reduced hardware costs, minimal maintenance expenses, and significantly lower power consumption compared to systems relying on independent drifters with satellite communication. By combining low power consumption with an optimized, compact integrated marine photovoltaic system, the drifters achieve unlimited operational autonomy. With the introduction of these new characteristics, the Smart Drifter Cluster goes beyond its primary function of mesoscale monitoring of marine currents. It becomes readily applicable to numerous civil applications, including recovering individuals and materials at sea, addressing pollutant spills, and tracking the dispersion of marine litter. An additional advantage of this remote monitoring and sensing system is its open-source hardware and software architecture. This fosters a citizen-science approach, enabling citizens to replicate, utilize, and contribute to the improvement of the system. Thus, within certain constraints of procedures and protocols, citizens can actively contribute to the generation of valuable data in this critical field.

Marine Litter Tracking System: A Case Study with Open-Source Technology and a Citizen Science-Based Approach.

It is well established that most of the plastic pollution found in the oceans is transported via rivers. Unfortunately, the main processes contributing to plastic and debris displacement through riparian systems is still poorly understood. The Marine Litter Drifter project from the Arno River aims at using modern consumer software and hardware technologies to track the movements of real anthropogenic marine debris (AMD) from rivers. The innovative "Marine Litter Trackers" (MLT) were utilized as they are reliable, robust, self-powered and they present almost no maintenance costs. Furthermore, they can be built not only by those trained in the field but also by those with no specific expertise, including high school students, simply by following the instructions. Five dispersion experiments were successfully conducted from April 2021 to December 2021, using different types of trackers in different seasons and weather conditions. The maximum distance tracked was 2845 km for a period of 94 days. The activity at sea was integrated by use of Lagrangian numerical models that also assisted in planning the deployments and the recovery of drifters. The observed tracking data in turn were used for calibration and validation, recursively improving their quality. The dynamics of marine litter (ML) dispersion in the Tyrrhenian Sea is also discussed, along with the potential for open-source approaches including the "citizen science" perspective for both improving big data collection and educating/awareness-raising on AMD issues.

Gaining new insights into macroplastic transport 'hotlines' and fine-scale retention-remobilisation using small floating high-resolution satellite drifters in the Chao Phraya River estuary of Bangkok.

In river plastic pollution research little is known about the detailed pathways and interruptions that occur during the journey of macroplastic debris (>5 cm) from land to sea. Data on fine-scale and high-accuracy transport trajectories and cycles of retention (when macroplastics are trapped, e.g. at a pier) and remobilisation is needed to inform global river plastic transport models as well as mechanical cleanup efforts. Though well established in the marine environment, the use of floating satellite drifters to understand macroplastic debris transport in tidal rivers and estuaries is in its infancy. Exploring the capacity to investigate fine-scale macroplastic debris-estuary interactions, this study brings together, on the one hand, a small, sensitive, floating satellite drifter with, on the other hand, the major riverine-marine habitat of the Chao Phraya River estuary at Bangkok, Thailand. The used grapefruit-sized drifters (n = 5) with minimal drogue (ρ ≈ 0.67 g/cm3) sent their positions at up to 4 m and 5 min spatiotemporal resolution via cellular GSM network for up to 48 days. This study indicates that river macroplastic debris transport 'hotlines' (positions where floating debris will likely pass by in a river) as well as retention-remobilisation cycles can be studied at fine scale. On their way through the river and gulf, covering between 9 and 696 km, drifters got stuck up to 23 times, spending 80% of their river lifetime in retention. Furthermore, it is outlined that the trajectories can be linked with environmental factors such as bathymetry and tides to more accurately model macroplastic debris behaviour in rivers. Finally, it is shown that trajectories crossing the riverine-marine continuum at the estuary can be accurately traced to support future investigations on the so far scarcely evidenced river mouth emissions of macroplastic debris.

Research on the Professional Mentality of Hengdian Drifter's.

Background: Hengdian drifters refer to outsiders who participate in shooting film and television dramas in Hengdian. It is a special group. Single access to information, precarious nature of work, unequal treatment of gender, constraints on development, and inadequate guarantee mechanisms are all to blame. Purpose: This paper proposes to improve the ecology of the different actor industries by implementing a precise assessme. Patients and methods: This study combines qualitative and quantitative research, adopts the questionnaire survey and semi-structured interview, and carries out fieldwork by personally experiencing the life of extras to study the ecological environment of the different actor industries and the professional mentality of extras. Before participating in the study, every participant would be offered an Informed Consent Form and all particpants were guaranteed anonymity and their response will be used for a specific academic study. The Ethics Committee of the Zhejiang Normal University's, Specific academic study that will be published online. College of Teacher Education approved the study and participation of concents under 18 and the study followed the Declaration of Helsinki. Results: There are gaps in social support.Little relevant policy support and financial support have not been implemented. Industry assessment criteria are not standardized.The level of digital management is low.It is difficult to guarantee the rights of mass actors. Conclusion: Implement a precise assessment system,develop a refined talent evaluation mechanism,Ensure the accuracy and transparency of the evaluation process.Establish digital service platforms,provide a new channel for the employment of artistic talents.Strengthen media publicity,strengthen policy support,raise social awareness.

Comparing the Currents Measured by CARTHE, CODE and SVP Drifters as a Function of Wind and Wave Conditions in the Southwestern Mediterranean Sea.

Instruments drifting at the ocean surface are quasi-Lagrangian, that is, they do not follow exactly the near-surface ocean currents. The currents measured by three commonly-used drifters (CARTHE, CODE and SVP) are compared in a wide range of sea state conditions (winds up to 17 m/s and significant wave height up to 3 m). Nearly collocated and simultaneous drifter measurements in the southwestern Mediterranean reveal that the CARTHE and CODE drifters measure the currents in the first meter below the surface in approximately the same way. When compared to SVP drogued at 15 m nominal depth, the CODE and CARTHE currents are essentially downwind (and down-wave), with a typical speed of 0.5-1% of the wind speed. However, there is a large scatter in velocity differences between CODE/CARTHE and SVP for all wind and sea state conditions encountered, principally due to vertical and horizontal shears not related to the wind. For the CODE drifter with wind speed larger than 10 m/s and significant wave height larger than 1 m, about 30-40% of this difference can be explained by Stokes drift.

Distribution and transport of microplastics in the upper 1150 m of the water column at the Eastern North Atlantic Subtropical Gyre, Canary Islands, Spain.

Nowadays it is widely known that pollution by microplastics (MP) at the open ocean covers immense areas. Buoyant plastics tend to accumulate in areas of convergence at the sea surface such as subtropical gyres, while non-buoyant plastics accumulate at the seafloor. However, previous studies have revealed that the total amount of plastic in the different oceans is not well correlated with the concentrations measured at the sea surface and the sea floor, evidencing a significant amount of missing plastic in the oceans. This deviation could be related to an underestimation of the role played by small fragments of plastic and fibers in the oceans. Furthermore, microplastic fragments with a density lower than the density of seawater have been gathered hundreds of meters below the sea surface in the Pacific Ocean due to their size and shape. The main objective of this study is to carry out, for the first time, an equivalent analysis along the water column for the Atlantic Ocean. In that sense, a total number of 51 samples were collected during four different oceanographic cruises between February and December 2019, from the sea surface down to 1150 m depth at the open ocean waters of the Canary Islands region (Spain). For each sample, 72 l of seawater were filtered on board with a mesh size of 100 µm, where the presence of microplastics has been clearly observed. Our results reveal the presence of microplastics at least up to 1150 m depth, at the Northeastern Atlantic Subtropical Gyre with noticeable seasonal differences. The spatial distribution of these small fragments and fibers at the water column is mainly related to the oceanic dynamics and mesoscale convective flows, overcoming the MP motion induced by their own buoyancy. Moreover, these microplastics have being transported by the ocean dynamics as passive drifters.

Trashing our own "backyard" - Investigating dispersal and accumulation of floating litter from coastal, riverine, and offshore sources in the German Bight using a citizen science-based wooden drifter recapture approach.

Understanding marine debris dispersal through drift buoys and numerical modelling is one focus of litter pollution research that can identify particularly affected regions and aid targeted clean-up efforts. This study assessed the dispersal and accumulation of floating litter from coastal, riverine, and offshore sources in the German Bight, based on ~33,000 reports of wooden drifters deployed between 2016 and 2019. The majority (66.6%) released along the Lower Saxony coast and the rivers Ems, Weser, and Elbe were first reported within ≤25 km, indicating that coastal and riverine litter sources largely pollute adjacent shorelines. Drifters from coastal sites and release points near the river mouths dispersed similarly far, occasionally crossing distances comparable to those deployed at sea, reaching Scandinavia and Great Britain within a few days or weeks. Small-scale clustering occurred in <2% of all locations where drifters had been reported. These findings and limitations of the methodological approach are discussed.

On the transport and landfall of marine oil spills, laboratory and field observations.

The dynamics of crude oil and different surface ocean drifters were compared to study the physical processes that govern the transport and landfall of marine oil spills. In a wave-tank experiment, drifters with drogue did not follow oil slicks. However, patches of undrogued drifters and thin bamboo plates did spread at the same rate and in the same direction as the crude oil slicks. Then, the trajectories of the Deepwater Horizon oil spill and 1300 drifters released near the spill source were investigated. Undrogued drifters were transported twice as fast as drogued drifters across the isobaths. 25% of the undrogued drifters landed, versus about 5% of the drogued ones, for the most part, on the same coastline locations where oil was found after Deepwater Horizon. Results highlight the importance of near surface gradients in controlling the cross-shelf transport and landing of surface material on the Gulf of Mexico's northern shores.

Measuring oil residence time with GPS-drifters, satellites, and Unmanned Aerial Systems (UAS).

As oil production worldwide continues to increase, particularly in the Gulf of Mexico, marine oil spill preparedness relies on deeper understanding of surface oil spill transport science. This paper describes experiments carried out on a chronic release of crude oil and aims to understand the residence time of oil slicks using a combination of remote sensing platforms and GPS tracked drifters. From April 2017 to August 2018, we performed multiple synchronized deployments of drogued and un-drogued drifters to monitor the life time (residence time) of the surface oil slicks originated from the MC20 spill site, located close to the Mississippi Delta. The hydrodynamic design of the two types of drifters allowed us to compare their performance differences. We found the un-drogued drifter to be more appropriate to measure the speed of oil transport. Drifter deployments under various wind conditions show that stronger winds lead to reduce the length of the slick, presumably because of an increase in the evaporation rate and entrainment of oil in the water produced by wave action. We have calculated the residence time of oil slicks at MC20 site to be between 4 and 28 h, with average wind amplitude between 3.8 and 8.8 m/s. These results demonstrate an inverse linear relationship between wind strength and residence time of the oil, and the average residence time of the oil from MC20 is 14.9 h.

Advances in the Application of Surface Drifters.

Surface drifting buoys, or drifters, are used in oceanographic and climate research, oil spill tracking, weather forecasting, search and rescue operations, calibration and validation of velocities from high-frequency radar and from altimeters, iceberg tracking, and support of offshore drilling operations. In this review, we present a brief history of drifters, from the message in a bottle to the latest satellite-tracked, multisensor drifters. We discuss the different types of drifters currently used for research and operations as well as drifter designs in development. We conclude with a discussion of the various properties that can be observed with drifters, with heavy emphasis on a critical process that cannot adequately be observed by any other instrument: dispersion in the upper ocean, driven by turbulence at scales from waves through the submesoscale to the large-scale geostrophic eddies.