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OBSERVER: Tracking oil spills with Copernicus

Oil spills can have a devastating and destructive impact on the oceans and marine wildlife, having been a major concern in the marine world for years.

Oil spills can occur as a result of accidents involving ships or oil rigs, or from illegal operational discharges. These incidents can be of different magnitudes: large scale oil spills, which fortunately do not occur so often, or smaller scale oil leakage or oil discharge incidents, which take place regularly. Every year, the amount of oil released (accidentally or deliberately) into the ocean by shipping vessels reaches thousands of tonnes. Copernicus data and services provide products and satellite-based information that helps national authorities detect, monitor and track potential ongoing oil spills, as well as support authorities in clean-up operations. Detections made by synthetic aperture radar (SAR) satellites such as Sentinel-1 are based on the processing of information on the roughness of the sea surface; floating oil has a dampening effect. However, other products or natural phenomena may cause the same effect. Until oil spills are verified, satellite detections are considered to be ‘possible’ oil spills. 

The Copernicus Maritime Surveillance Service — supporting EU authorities in near real time

The Copernicus Maritime Surveillance Service (CMS) provides the detection of discharges of oil, assist in identifying the polluting vessels, as well as monitor the evolution of accidental spills during emergencies. It is implemented by the European Maritime Safety Agency (EMSA) on behalf of DG DEFIS and is one of the three components of the Copernicus Security Service. Apart from maritime pollution monitoring, CMS provides a range of other functions to support maritime monitoring and understanding human activities at sea, such as maritime safety and security, situational awareness for fisheries control, customs, law enforcement and many other activities. The CMS service is offered to national authorities and EU bodies working in the maritime domain and covers not only European waters but maritime areas of European interest anywhere in the world. The CleanSeaNet (CSN) service operated by EMSA provides pollution monitoring in European waters (see below), while the CMS service provides this support further afield in areas of European interest.

Since 2007, EMSA has been operating CleanSeaNet, a service which combines synthetic aperture radar (SAR) and optical data with other kinds of information (for example, vessel identification and position information, behavioural patterns and intelligence from users) to monitor oil spills and detect potentially polluting vessels. SAR satellite images are useful to detect oil spills and possible illegal discharges from ships as they appear as long, linear dark shapes in the SAR image, while vessels and oil platforms appear as bright white spots. In 2015, CleanSeaNet started using Copernicus Sentinel-1 satellite imagery, which significantly improved the level of satellite coverage over European waters and reduced costs at the same time, whereas previously available data have to be purchased from commercial operators. Integration of Copernicus Sentinel-1 data improved the detection capabilities of CleanSeaNet and increased the volume of accessible imagery, which allowed for the detection of smaller spills than before.

A key feature of both CMS and CleanSeaNet is that services are delivered in near real time. From the moment of satellite overpass, a standard-sized image in European waters can be acquired, processed, analysed and delivered to the end user via a secure interface within 20 minutes.  

Supporting the response to accidents and emergencies 

When the Italian cruise ship Costa Concordia ran aground near the island of Giglio (Italy) in January 2012, it was carrying around 2,400 tonnes of heavy fuel oil. Apart from being a human tragedy, the accident also posed a significant environmental risk. The shipwreck was lying in a protected marine area, home to many fish and bird species, as well as a whale sanctuary. The full tanks could have leaked into the sea with heavy environmental consequences and a very difficult clean-up operation. When such an accident occurs, the authorities need information about the estimated volume of the oil leakage and the predicted behaviour of the spill in order to prevent further environmental degradation and plan clean-up operations.

In these cases, Copernicus can help. Oil spills appear on satellite SAR imagery as black spots concentrated in the area of the incident. Therefore, Copernicus Sentinel satellite imagery and Copernicus Services’ pollution monitoring capabilities can assist authorities in detecting and monitoring the spread of oil. Furthermore, ocean and atmospheric currents affect the way oil disperses into the ocean. Copernicus Services’ oceanic and atmospheric models can also help predict the behaviour of the oil spill.

In the Costa Concordia incident, Copernicus data and models helped the Italian Coast Guard prepare preventive measures and plan for clean-up activities in the event of oil leakage. Following the initial emergency response that aimed to save the lives of the passengers and cruise ship crew, the next task was to help prevent the environmental disaster which would occur if the oil leaked into the surrounding area. Copernicus supported the Italian Coast Guard with daily valuable information through an application developed by a joint team from the Italian National Institute of Geophysics and Volcanology (Istituto Nazionale di Geofisica e Vulcanologia — INGV), the Euro-Mediterranean Centre on Climate Change (Centro Euro-Mediterraneo sui Cambiamenti Climatici — CMCC) and the University of Bologna.

On the left, ocean current forecast for the Giglio island area based on high-resolution satellite data. On the right, the surface oil concentration in tons/km² predicted for the area around the Costa Concordia cruise ship. The available scenario predictions allowed authorities to better plan risk mitigation measures. (Source: MyOcean by courtesy of INGV, Copernicus Brief ISSUE 41 / DECEMBER 2013)
On the left, ocean current forecast for the Giglio island area based on high-resolution satellite data. On the right, the surface oil concentration in tons/km² predicted for the area around the Costa Concordia cruise ship. The available scenario predictions allowed authorities to better plan risk mitigation measures. (Source: MyOcean by courtesy of INGV, Copernicus Brief ISSUE 41 / DECEMBER 2013)

The application used ocean current data in the Mediterranean Sea from the Copernicus Marine Service to simulate the possible fuel dispersion in case of leakage.

Unfortunately, in some instances, the undertaken efforts are no longer about helping predict the extent of a potential leak, but about helping clean-up and monitoring operations after an oil spill has occurred. The island of Mauritius experienced such an emergency in July 2020, when a vessel ran aground on a coral reef on Mauritius’ southeast coast and began leaking tonnes of oil into the Indian Ocean. The MV Wakashio vessel carried nearly 4,000 tonnes of oil, a quarter of which leaked into the ocean and polluted the nearby coral reefs, beaches and lagoons.

MV Wakashio stranded close to Pointe d’Esny, an important wetland area. The oil slick can be seen as a thin, black line surrounded by the bright turquoise colours of the Indian Ocean. Oil is visible near the vessel, as well as other locations around the lagoon. This image was captured on 11 August 2020 by the Copernicus Sentinel-2 mission. (Credit: Modified Copernicus Sentinel data (2020) processed by ESA. Source: SciTechDaily)
MV Wakashio stranded close to Pointe d’Esny, an important wetland area. The oil slick can be seen as a thin, black line surrounded by the bright turquoise colours of the Indian Ocean. Oil is visible near the vessel, as well as other locations around the lagoon. This image was captured on 11 August 2020 by the Copernicus Sentinel-2 mission. (Credit: Modified Copernicus Sentinel data (2020) processed by ESA. Source: SciTechDaily)

The island declared a “state of environmental emergency” and the Copernicus Maritime Surveillance Service (CMS) was activated on 6 August 2020 by the EU’s Emergency Response and Coordination Centre (ERCC) and the EU Delegation, following the detection of an oil spill from the bulk carrier of an estimated amount of 1,000 metric tonnes of fuel. CMS provided SAR and optical imagery to support the counter pollution and salvage operations.

Oil detected along the coastline following the grounding of the MV Wakashio, displayed in one of the SAR images acquired for the Copernicus Maritime Surveillance Service.
Oil detected along the coastline following the grounding of the MV Wakashio, displayed in one of the SAR images acquired for the Copernicus Maritime Surveillance Service.

Copernicus Sentinel-2 imagery was also used as part of the activation of the International Charter Space and Major Disasters, to monitor the ongoing spill and derive a preliminary assessment of the pollution.

Comparison of the pre-event and post-event Sentinel-2 image and the subsequent analysis of the detected oil spill. (Source: Preliminary satellite-based oil spill assessment, Reef of Pointe d'Esny, Republic of Mauritius)

Comparison of the pre-event and post-event Sentinel-2 image and the subsequent analysis of the detected oil spill. (Source: Preliminary satellite-based oil spill assessment, Reef of Pointe d'Esny, Republic of Mauritius)
Comparison of the pre-event and post-event Sentinel-2 image and the subsequent analysis of the detected oil spill. (Source: Preliminary satellite-based oil spill assessment, Reef of Pointe d'Esny, Republic of Mauritius)

Similarly, Copernicus monitored an oil spill in the Red Sea which resulted from the damage of an Iranian-owned oil tanker in October 2019. Copernicus Sentinel-1, Sentinel-2 and Sentinel-3 satellite imagery was used to track the oil spill, in combination with ocean current models from the Copernicus Marine Service and atmospheric models (e.g. on surface winds) from the Copernicus Atmosphere Monitoring Service (CAMS).

Copernicus Sentinel-1 images acquired on 13 (west) and 14 (east) October 2019. The tanker Sabiti apparently underwent damage at the location of the origin of the long oil spill. The position of the tanker is represented by the small white circle, located in the northwest. The undulations of the oil slick are due to complex ocean currents in the Red Sea and, to a lesser extent, to surface winds. (Source: Copernicus Sentinels observe extensive oil spill in the Red Sea. Credit: Contains modified Copernicus Sentinel data (2019)/processed by VisioTerra)
Copernicus Sentinel-1 images acquired on 13 (west) and 14 (east) October 2019. The tanker Sabiti apparently underwent damage at the location of the origin of the long oil spill. The position of the tanker is represented by the small white circle, located in the northwest. The undulations of the oil slick are due to complex ocean currents in the Red Sea and, to a lesser extent, to surface winds. (Source: Copernicus Sentinels observe extensive oil spill in the Red Sea. Credit: Contains modified Copernicus Sentinel data (2019)/processed by VisioTerra)

Serge Riazanoff, CEO of VisioTerra, the company that processed the data, had stated: "This example of major pollution in the Red Sea demonstrates the effectiveness and complementarity of Copernicus Sentinel data. The high temporal resolution of the observations made it possible to follow the evolution of the oil slick from day to day.”

Following the 2019 sinking of the vessel Grande America, which carried large quantities of fuel oil and hazardous substances on board, 55 satellite images — including 31 Sentinel-1 images — were acquired through the EMSA CleanSeaNet service to monitor the resulting spill. Following the collision of two vessels near Corsica in 2018, CleanSeaNet had provided images to assist the French authorities monitoring the spread of the spill.

Following the collision of two vessels near Corsica and the resulting oil spill, satellite images were used to track the overall development of the spill. (Source: EMSA, 2018)
Following the collision of two vessels near Corsica and the resulting oil spill, satellite images were used to track the overall development of the spill. (Source: EMSA, 2018)

There are many other examples of the application of Copernicus Services satellite data and imagery in the event of an oil spill (e.g. a recent oil spill in the Mediterranean Sea, near Israel), or where atmospheric or marine data modelling is used as a reference point for oil spill drift modelling (e.g. Copernicus Marine Mediterranean sea models are used by MONGOOS — the Mediterranean Operational Network for the Global Ocean Observing System.

Keeping an eye on potential polluters

Deliberate illegal discharge of oil by shipping vessels is another type of incident that causes oil pollution. Rapid detection of the discharge incident improves the likelihood that coast guards will catch the polluters. When it comes to monitoring oil spills in the ocean, satellite-based services increase the efficiency of other surveillance assets, such as ships or aircrafts, by enabling very wide coverage (one single image can cover more than 500,000 km²) and pinpoint the locations to be verified, thus  reducing the monitoring costs of Member States.

Illegal discharge of oil from a vessel captured by a Copernicus Sentinel-1 SAR image in 2019. The vessel appears as a bright spot, whereas the oil discharge appears as a long, linear, dark shape. (Source: Copernicus Maritime Surveillance Overview)
Illegal discharge of oil from a vessel captured by a Copernicus Sentinel-1 SAR image in 2019. The vessel appears as a bright spot, whereas the oil discharge appears as a long, linear, dark shape. (Source: Copernicus Maritime Surveillance Overview)

When a possible oil spill is detected by the CleanSeaNet or CMS, the authorities are alerted of the situation, usually within 20 minutes of the satellite acquisition. The potential oil spills identified by satellites are classified according to the probability that an observed dark feature in the satellite image is related to the actual presence of an oil spill, otherwise referred to as their confidence level.

Detection statistics for CleanSeaNet in 2020, with dots that represent spills with a higher detection confidence level in red and a lower detection confidence level in green. (Source: EMSA)
Detection statistics for CleanSeaNet in 2020, with dots that represent spills with a higher detection confidence level in red and a lower detection confidence level in green. (Source: EMSA)

The transposition of the position of the oil spill using the vessel position tracking data helps to identify the nearby vessels that might be the potential polluters. The near-real-time warning enables authorities to take rapid action, and, for example, send assets to the scene or inspect the suspicious vessel or vessels at the next port of call, which increases the likelihood of catching the polluter red-handed. CleanSeaNet provides more than 8,000 satellite images per year to 35 coastal states and helps to strengthen their response to illegal discharges or accidental spills. Of the 35 coastal states, 23 are within the coastal European Union (EU) region, 2 are members of the European Free Trade Association (EFTA), 3 are candidate countries, and 7 are countries relevant in the context of the European Neighbourhood Policy (ENP) SAFEMED IV and BCSEA projects.

Potential deliberate discharge of oil by a vessel captured on a Sentinel-1 image. Vessel position data from the EMSA systems shows the track of the vessel identified as a possible polluter. The potential spill can be seen clearly as a dark feature on the sea surface surrounded by a blue polygon that closely follows the vessel track. (Source: EMSA, 2020)
Potential deliberate discharge of oil by a vessel captured on a Sentinel-1 image. Vessel position data from the EMSA systems shows the track of the vessel identified as a possible polluter. The potential spill can be seen clearly as a dark feature on the sea surface surrounded by a blue polygon that closely follows the vessel track. (Source: EMSA, 2020)

The CleanSeaNet service is used for routine monitoring of large maritime areas on a regular basis. Depending on the nature of the request, regular pollution monitoring for illegal discharges is also possible through the CMS pollution monitoring service. For example, CMS is used by the Joint Arctic Command (JACO) of the Danish Defence Command, whose main mission is to monitor the seas around Greenland. Since 2018, CMS has provided JACO with regular satellite imagery acquired across the predefined areas of interest in order to detect possible illegal discharges. CMS’s detection capabilities are integrated into JACO’s pollution detection and response chain, which aims to ensure the successful prosecution of the violator.

Safeguarding the world’s seas

Oil spills can have important and devastating environmental and economic effects. It is thus vital for national and international authorities to have access to reliable and timely data to track and monitor (potential) oil spills and potential polluters. Luckily, the Copernicus programme and its services can help keep an eye on the world’s seas by providing models to track and predict how a potential leak would spread, assisting in clean-up operations and detecting the illegal discharge of oil.