The source of the massive oil spill affecting Brazil remains unclear, but unusual tanker activity raises questions.
For months now, oil has been washing up on the beaches of northeast Brazil. The quantity of oil, the large area affected, and the length of time oil has appeared, have generated international news coverage and concern. Government officials, scientists and non-governmental organizations around the world — including SkyTruth — have been trying to identify the source of the pollution; so far, unsuccessfully. Brazilian researchers have identified a likely location for the origin of the spill based on ocean currents. The oil is a heavy consistency that floats below the surface of the water and Brazilian researchers and government officials have claimed that it is likely from Venezuela, although they haven’t published the chemical analysis data to support this.At SkyTruth we have been examining available satellite imagery and evaluating some of the theories put forward on the origin of the spill. We haven’t seen any convincing evidence of oil slicks or sources on the images, and we don’t agree with analyses published by others (here and here) that claim to have solved the mystery. I recently decided to take a look at AIS (Automatic Identification System) ship-tracking data in the region that Brazilian researchers identified to be the likely origin of the spill. When I examined the AIS data, I found some unusual behavior by oil tankers passing through the area.
AIS is a system in which vessels at sea transmit their location at regular intervals via VHF radio. Initially designed for collision avoidance, this location data is also picked up by satellites and provides a global record of vessel movements. I was aided by Global Fishing Watch’s automated modeling of AIS tracks, developed by data scientist Nate Miller, which identifies loitering events, that is, locations where vessels have essentially come to a stop, and are drifting out at sea. Tankers and cargo ships normally maintain a relatively constant transit speed as they are moving from their point of origin to their destination port. Ships may stop out at sea for a number of reasons, including engine problems, waiting for entry authorization at a port, or even at-sea transfers of cargo or refueling. But spending more than 24 hours adrift at sea represents a financial loss for a tanker and would suggest unusual circumstances.
Of hundreds of tankers that moved through the area in the months before the oil was reported, a handful stood out for having lengthy loitering events near the likely area of origin for the spill. One particular tanker, rather than proceeding directly on a course from Spain to Argentina, stopped for two extended periods (each for approximately 14 hours) just within Brazil’s Exclusive Economic Zone (the EEZ area extends up to 200 nautical miles from shore). The tanker I identified with these unusual loitering events is The Amigo, a 133-meter vessel listed as an Asphalt/Bitumen tanker and flagged to the Marshall Islands.
We checked for satellite imagery in the area where the vessel was drifting (July 24 – 26) and unfortunately didn’t turn anything up. So any possible association between this tanker and the oil spill is purely speculative. However, some of the circumstances of the vessel’s operation fit with theories on the source of the spill so we think its activities should be scrutinized further.
The Amigo is an unusual tanker in that it is outfitted to maintain its cargo at high temperature to keep it from solidifying. When the tanker passed through Brazilian waters off Brazil’s northeast coast, it was en route from Cadiz, Spain to a port near Buenos Aires, Argentina. The loitering events occurred between July 24 and July 26 before the vessel proceeded to Argentina. Port records show that on August 10 the vessel delivered 14,000 tons of bitumen (or at least it was scheduled to offload that quantity of product). AIS confirms that the tanker reached dock in Campana, Argentina on August 10.
The tanker was coming from Cadiz, Spain though we don’t know if the asphalt was actually from Spain or what quantity was loaded at the port facility in Cadiz. Earlier this year the vessel visited Venezuelan ports and imported Venezuelan asphalt to the US. This article from March mentions The Amigo in the context of US sanctions against Venezuela that were coming into force. Could The Amigo have been carrying a cargo of asphalt that originated in Venezuela?
The terms asphalt and bitumen appear to be used interchangeably to describe a semi-solid form of petroleum. High heat tankers like The Amigo must maintain their cargo at an elevated temperature so that it does not solidify, and can be pumped out of the vessel. Problems with heating might result in product remaining in one of the ship’s tanks and needing to be flushed out. Even under normal operations, heavy oil residue can build up in the cargo tanks and needs to be washed out or removed to free up usable space. International law requires that this be done in port where the oily sludge can be treated, but many ports lack the necessary treatment facilities. If somehow asphalt did end up being discharged directly into the ocean it would be expected to drift below the surface in warm equatorial waters. This might not generate a large surface oil slick that could be seen on satellite images, possibly explaining our frustration here at SkyTruth.
As mentioned, there are some legitimate reasons for a tanker to be drifting out at sea. But we think it is fair to pose some further questions about this vessel given the severity of the spill in Brazil. What prompted the vessel to halt its normal transit off Brazil? What was the origin of the asphalt carried by the vessel and what quantities were loaded and offloaded? Could the chemical properties of the oil found on Brazilian beaches match this cargo, or any oily residue remaining in The Amigo’s cargo tanks?
But it’s not just The Amigo that’s raising questions for us. We’ve detected loitering events by other tankers in recent months (as shown on the map above and in the table below). We’ve found evidence of likely bilge-dumping by a few vessels in the area. And we’ve noticed that more than a dozen tankers operating in this area turn their AIS off while at sea, apparently in violation of international maritime safety law.
We hope to find out answers to some of these questions soon, and we will continue to investigate all available data that might help to identify the origin of this devastating oil spill. One problem is very clear: we don’t know everything we need to know about the tanker activity near Brazil, and in many other parts of the ocean.