Session Chairs: Nikolai Maximenko, University of Hawaii; Delwyn Moller, Remote Sensing Solutions; Bertrand Chapron, IFREMER; Paolo Corradi, ESTEC; Victor Martinez Vicente, Plymouth Marine Laboratory

This session is catered to engineers, scientists and responders who will overview remote technologies available for surveillance of marine debris and factors, controlling its drift, and present existing products, results of their applications and ideas for future missions.

 Traditional methods based on counting marine debris items provide fragmentary information not sufficient to help close regional and global balances of the plastic pollution. Only remote sensing, covering great areas, can fill gaps in sparse in situ point observations. Complex composition of debris, including broad ranges of sizes, shapes, and chemical composition, makes it not possible to observe all types with any single sensor.

This session invites presentations demonstrating feasibility or publishing new ideas of remote sensing technologies that can help identify, quantify, and/or track various types of plastic pollution or other types of marine debris on the ocean surface or on the shoreline.

Understanding the drift of marine debris in the ocean requires good knowledge of the dynamics of the ocean-atmosphere surface circulation and is important for a growing list of operational activities, such as search and rescue and response to oil spills. Presently, even large objects can’t be followed by the satellite observing system. Examples include missing flight MH370 and millions of tons of debris from the 2011 tsunami in Japan and 2004 tsunami in Indonesia, whose pathways and fate are not known or known very vaguely.

Applications, derived from satellite measurements of oceanic and atmospheric variables, calibrated with the data of marine debris and used to advance the understanding of marine debris drift, are also welcome at our session.




Hyperspectral airborne shortwave infrared imager captures floating ocean plastics in the Great Pacific Garbage Patch

presenting: Shungudzemwoyo Garaba (The Ocean Cleanup Foundation, United States); authors: Shungudzemwoyo Garaba (The Ocean Cleanup Foundation, United States), Julia Reisser (The Ocean Cleanup Foundation), Jen Aitken (Teledyne Optech Inc), Heidi Dierssen (University of Connecticut), Laurent Lebreton (The Ocean Cleanup Foundation), Robert Marthouse (Teledyne Optech Inc.), Boyan Slat (The Ocean Cleanup Foundation)

We present one of the first aerial remote sensing expeditions to use state-of-the-art technology for high spatial resolution and spectral observations of floating ocean plastics. An integrated measuring instrument package including a CZMIL bathymetric lidar, a hyperspectral shortwave infrared (SWIR) imager and a high spatial resolution RGB frame camera was mounted on a manned C-130 Hercules aircraft. The aircraft flew over the oceanic accumulation zone known as ‘Great Pacific Garbage Patch’ (GPGP), located between California and Hawaii, USA. Imagery was gathered over two flights conducted in October 2016, both flights lasting over ten hours with 2.5 hours of survey data collection. Flying at an altitude of 400 m above the ocean a total surface area covering 311 km2, was surveyed at 140 knots speed. Imagery spatial resolution was 0.5 x 1.2 m pixels for the shortwave infrared hyperspectral imager (SASI-600 SWIR, 950-2450 nm, 100 bands, push broom line scanner) and 0.10 m for the Optech CS-4800i, 16 MP RGB frame camera (one frame per second). We investigated debris larger than 0.1 m (N = 118) from the 150 debris automatically identified in the RGB mosaics. Spectral information was retrieved from the SASI SWIR imagery, debris examined had unique features common to synthetic polymers, making it possible to discriminate pixels as containing water, surface reflected glint and ocean plastic. We showcase the capability of airborne remote sensing of plastic debris in the aquatic environment. These findings echo the need for algorithms, spectral reference libraries and tools to advance remote sensing technology for observing, classifying as well as quantifying ocean plastics.


Optical remote sensing of marine litter: review of mission requirements and current potential detection techniques

presenting: Victor Martinez-Vicente (Plymouth Marine Laboratory, United Kingdom); authors: Victor Martinez-Vicente (Plymouth Marine Laboratory, United Kingdom), James Clark (Plymouth Marine Laboratory), Penelope Lindeque (Plymouth Marine Laboratory), Stefan Simis (Plymouth Marine Laboratory), Rory Donnelly (Plymouth Marine Laboratory), Paolo Corradi (European Space Agency), Bertrand Chapron (IFREMER), Yi Chao (Remote Sensing Solutions, Inc), Nikolai Maximenko (University of Hawaii)

At a global scale, there is a need for an accurate description of the distribution of human produced litter. Plastics are the largest component of human produced litter in the aquatic environment (from oceans and coastal waters to rivers and lakes). Any improvement on the global quantification of plastics in the aquatic environment would have a significant impact in addressing both fundamental scientific questions such as improving the quantification of plastic pools and fluxes, validating plastic accumulation models, as well as providing tools for environmental monitoring for the benefit of the society, such as informing on sources and sinks for mitigating action.

It is postulated that global observations of the litter problem could be obtained by using support from remote sensors. Progress in this direction has been encouraged by a number of space agencies. The ESA funded project OptiMAL (Optical methods for MArine Litter detection), reviews different observational scenarios for marine litter detection, focussing on optical remote sensing techniques. In particular, this initial review covers two scenarios for plastic litter detection: microplastics (diameter < 5 mm) in the upper layers of the aquatic environment, and macroplastics accumulated on shorelines.

The microplastics distribution in the oceans has been described using several ocean circulation models, highlighting significant discrepancies in their predictions. OptiMAL explores the model requirements for remote sensing products that would help reduce model uncertainty.

The accumulation of plastics on the shore has been monitored using varying protocols by agencies and citizens, and there is a need to unify quantification methods that can also be used in areas that are remote or difficult to access. Requirements for the operational use of remote sensing.


The Debris and Small Object Mapping Active Imaging System

presenting: Delwyn Moller (Remote Sensing Solutions, United States); authors: Delwyn Moller (Remote Sensing Solutions, United States), James Carswell (Remote Sensing Solutions), Brian Pollard (Remote Sensing Solutions), Yi Chao (Remote Sensing Solutions)

Because of the broad diversity of types of objects, floating on the ocean surface, and sensitivity of observations to many factors, today marine debris cannot be systematically quantified by existing observing systems. Neither sources, distribution, total amount, life cycle, nor sinks of marine debris are currently understood. To address these deficits in understanding, there is interest in the potential of remote sensing from a variety of technologies. For example, a NASA-funded workshop at the University of Hawaii, Manoa (1/2016), assessed existing and emerging remote-sensing technologies with the potential to observe or infer marine debris on the global scale. A workshop recommendation was for suborbital and laboratory experiments to test various methodologies and to prove the concept(s) with future satellite missions in mind.

Aligned with this recommendation, NOAA has funded development of the Debris and Small Object Mapping (DSOM) system, can be configured as a multi-baseline interferometric synthetic aperture radar array for detection and mapping of manmade and natural debris and “small” objects in the maritime environment. The DSOM sensor concept will acquire multi-dimensional (spatial and temporal) measurements that will provide unique information for detecting a broad range of debris types and small objects in marine environments over over a large range of environmental and surface conditions. The DSOM will be deployed and operated in such a way that it serves as an interferometric multiple-aperture SAR simulator. Our data analysis will entail algorithm development and system trades for detection and characterization over a variety of oceanic wind/wave conditions and for a variety of debris materials and surface expressions.


Using Ocean Surface Currents and Winds to Track Marine Debris

presenting: Ernesto Rodriguez (Jet Propulsion Laboratory?Caltech, United States); authors: Ernesto Rodriguez (Jet Propulsion Laboratory?Caltech, United States), Dragana Perkovic-Martin, Alexander Wineteer, Bryan Stiles

Ocean surface currents and winds play a primary role in the transport and dispersal of marine debris. Satellite altimetry is an approach to estimating ocean currents, which can only estimate the geostrophic component, and must be complimented by modeled wind-driven currents, using scatterometer winds. This is the approach taken by surface current products such as OSCAR (Ocean Surface Currents Real-time). However, it is limited by spatial resolution and cannot represent the small mesoscales, which are responsible for forming attractors that concentrate marine debris.

Here, we present an alternative method for simultaneous mapping of ocean winds and currents using Doppler scatterometry. Doppler scatterometry relies on a coherent radar system with a rotating pencil beam antenna to simultaneously measure the backscattered power and Doppler frequency shift. The two are then converted into vector wind and surface current estimates over wide swaths. JPL/NASA has developed a proof-of-concept instrument called DopplerScatt. It is an airborne Ka-band scatterometer capable of 200-m resolution measurements of winds and currents over a 25 km swath, in a single aircraft pass.

In this talk, we report on the comparison of DopplerScatt measurements and surface drifters from the recent SPLASH (Submesoscale Processes and Lagrangian Analysis of the Shelf) campaign, where about 500 surface drifters (drogued at ~0.75m) were released and measured over a period of weeks. We also report on how this technique can be scaled to a spaceborne measurement, able to produce global simultaneous estimates of winds and currents.


Multi-sensor remote sensing approach to marine litter mapping

presenting: Laia Romero (isardSAT, Spain); authors: Laia Romero (isardSAT, Spain), Juan Baztán (Université de Versailles Saint-Quentin-en-Yvelines), Mathias Bochow (GFZ German Research Centre for Geosciences), Maria Jose Escorihuela (isardSAT), Lucile Gaultier (OceanDataLab), Thierry Huck (Univ. Brest, Ifremer, CNRS/IRD/LOPS), Christophe Maes (Univ. Brest, Ifremer, CNRS/IRD/LOPS), Eduard Makhoul (isardSAT), Mònica Roca (isardSAT)

While the knowledge associated with the marine litter challenge is increasing rapidly, there are still many unknowns regarding the contribution of satellite technologies to the solution. Complex mapping requirements are withdrawn from the great variety of scenarios where plastic is found in aquatic ecosystems. There is no single technology able to map marine litter alone. Nonetheless, a series of remote sensing technologies exist today that are able to tackle the mapping of marine litter, directly and indirectly. Optical technologies can be used for the direct detection of high densities of plastics in cloud-free areas, and the correlation found between water quality parameters and microplastics motivates indirect assessment. Plastics show significant features in the 0.4–2.8 μm region of the spectrum, where most hyperspectral systems operate, and Fourier Infrared Spectroscopy has been suggested for the classification of plastic composition, while Raman spectroscopy could measure partially submerged debris in shallow waters. Within microwave technologies, SAR sensors are capable of detecting surfactants such as biogenic films, and target-like derelict fishing gear and bigger items, by polarimetry and interferometry; like SAR, altimetry could also detect marine litter as it might have an effect on reflectivity, and radiometers with high temporal resolution can be useful for the tracking of water masses containing debris. A multi-sensor approach is proposed for the mapping of marine litter in a broad sense, according to the characterization of different scenarios. In order to delineate pathways, and to provide information over spatio-temporal gaps in the remote sensing methods, the use of ocean models that resolve the small-scale dynamics of the upper ocean, and backward computations with ground-truth data are proposed.


An innovative machine learning technique to retrieve omni-situ ocean surface currents measurements: a global and high resolution ocean surface circulation schema

presenting: Yann Guichoux (eOdyn, France); authors: Yann Guichoux (eOdyn, France), clement le goff (eOdyn)

Our presentation focus on the description of transformative technique allowing omni-situ ocean surface currents measurements relying on environmental data sets and ship motions data analytics. The technology make it possible to retrieve real time and historical ocean surface currents information at a global scale.

First the technique is introduced, how machine learning on environmental data sets and ship motions can produce omni-situ ocean surface currents. Performances are assessed basing on West Brittany, a well-documented area, comparing HF radar measurement with eOdyn products. Technology’ fields of application, as well as its limitations and development status are introduced.

Then, the surface circulation in south Africa is investigated using this innovative technique and compared to numerical model outputs and drifters trajectories. A three months omni-situ ocean surface currents climatology is compared to the bottom topography. This comparison clearly shows a good correlation between omni-situ surface currents and bathymetry.

At last, new possibilities allowed by this technique, such as micro-platics drifts analysis, are highlighted.


RESMALI: Towards a better understanding of marine litter signature from space

presenting: Manuel Arias (ARGANS Ltd, United Kingdom); authors: Manuel Arias (ARGANS Ltd, United Kingdom), Julia Reisser (The Ocean CleanUp), Laurent Lebreton (The Ocean CleanUp), Andres Cozar (University of Cadiz), Jennifer Aitken (Teledyne OpTech Ltd), Shungu Garaba (University of Connecticut), Gullaume Bonnery (Airbus Defence & Space), Paolo Corradi (European Space Agency)

Marine Litter (ML) is a major environmental issue requiring deeper insights from the scientific community for policy makers and enforcers to manage and mitigate these contaminants. Collection of data is an important step towards solving the ML issue. The scientific community has already pointed out that remote sensing techniques may be the best approach to get a synoptic and routine monitoring. RESMALI project consists on a feasibility study for a mission concept devoted to remotely sense ocean plastics using satellites as platforms. Given that wide range of ML sizes, from microns to meters, remote sensors are likely to only be able to observe ML particles or groups of particles above a certain size. In this regard, it is interesting to know the minimum observable ML plastic/group of ML size and the fraction of the total ML stock that can be observed. Reference curves of the fraction of the total ML stock observed with proposed technologies, once the size limit of each technology is determined, are required. To build some of such curves and define additional mission requirements, the authors are carrying out an experimental set to expand the existing knowledge of plastic ML in the SWIR band by hyperspectral methods. The experiments is performed using both “natural” and “artificial” ML samples with a varied range of sizes and classified by their composition. The data allows for the generation of a spectral library that can be used in numerical simulations via LibRadTran to determine the expected signature of ML at TOA level, depending on concentration and composition. The simulations aid to find out thresholds values for these parameters for a potential passive hyperspectral radiometric instrument what also includes, but is not limited to, optimal altitude, spectral sensitivity, and instrumental viewing angle.


Progress in remote sensing of marine debris

presenting: Nikolai Maximenko (University of Hawaii, United States); authors: Nikolai Maximenko (University of Hawaii, United States)

This poster presentation is intended to provide concise overview of recent initiatives, studies, and developments that advance applications of remote sensing to all aspects of the problem of marine debris. It will include a short list of past and future meetings and programs that help to build the community of specialists. Additional highlights will be invited from active projects, conducted by the session participants and unrepresented groups.