Forensic oceanography: challenges in police search operation

Sophisticated modelling technology to help recover bodies is a fast-emerging area of oceanography. It is vital work which can give closure to those left behind, explains Jon Rees, FIMarEST, at the Centre for Environment, Fisheries and Aquaculture Science.

From Lego bricks and tropical fruits to cocaine and oil spills, our seas carry a wide range of materials and substances vast distances.

Tracking and modelling these seaborne journeys can be vital, whether it’s to prevent pollution, fight crime or remove hazards to shipping.

In a case that resonates today, when a dead swan on a beach in Scotland tested positive for the deadly H5N1 strain of bird flu in 2006, scientific advisors were keen to know where it had originated.

Using sophisticated modelling, oceanographers at the Centre for Environment, Fisheries and Aquaculture Science (CEFAS), a UK government agency that regularly works with other government organisations such as Defra, MMO, FSA and coastguard agency MCA, were able to identify the bird had died in the central North Sea and washed ashore.

Tragically, however, this oceanographic detective work often includes tracing dead bodies, with Jon Rees, Principal Physical Oceanographer at CEFAS, saying they get requests on a fortnightly basis to help recover missing persons.

These can be maritime accidents at sea, anglers washed away, or suicides, which typically surge around Christmas.

“Sadly, we get called in when the MCA search and rescue operation is stepped down,” says Rees. “The police will also call us in if there’s a suicide or another incident where someone goes into the water.”

CEFAS helps police refine search locations once a body has entered the water. “The challenge from an oceanographer’s point of view is to characterise the missing person to work out their gravity, which will depend on their size, height, weight and clothing – heavy coats, denim and boots will sink more easily – and whether, in the case of suicide, they’ve added stones to their pockets,” explained Rees.

Stomach contents are another important signal of buoyancy.

“These can be a key factor in terms of bringing bodies back up to the surface as micro-bacterial activity will over time produce gases, which will change a person’s gravity,” he explains.

“It depends on what they eat as to whether this process is faster or slower. This is an area for research, and we’re working with Reading University to get a programme off the ground.”

Models, such as this one showing the Isle of Wight, can reveal where objects or materials originated from

Prediction accuracy

Given the range of variables involved, the modelling can be surprisingly accurate.  Called in to help with the search for a missing person who had jumped into the Firth of Forth near Edinburgh, Scotland, Rees was able to estimate not just the likely location of the beaching but also the approximate timing.

“The person had been identified on CCTV, so we had a time for hitting the water and good pictures to guess gravity,” says Rees. “We predicted beaching would be three days forward on a certain beach, so we advised the police to stand down until then. They then found the body on that particular beach, closing the case and hopefully helping to give some closure for the family. It was a case where everything worked as it should.”

The savings in terms of police resources can be significant. “In one case, where a missing person had fallen into a loch in the Scottish Highlands, we advised the police to stand down the search for 28 days,” recalls Rees.

“Buoyancy was established as negative due to heavy, wet weather gear and boots, and we knew it would take a fairly long time for the individual to come up to the surface. When the search resumed, the missing person was recovered within the search area and had likely only been ashore two days. It meant the police force had not spent the whole month searching that hugely complex area around the west coast.”

The model doesn’t always deliver, however. In one missing person case, the body was predicted to have headed down an estuary but was instead recovered upstream. “It was 180-degrees wrong in this case and feedback suggested the body may have been caught on a tree. These obstacles in the water column can be an issue.”

Another case, off the south coast of England was complicated by very strong and dynamic currents around a headland. “I predicted the missing person would be caught in one of these gyres, which act like a giant washing machine and can spit you out in any direction, making it very unpredictable, but actually the body was recovered about 250 metres from where they went into the water, and it’s likely they got caught on the seabed.”

Lost to the sea

More difficult are those cases where no body is recovered.

One missing person, who jumped from the Firth of Forth Bridge, was identified as having been swept straight out to sea. “It’s the worst-case scenario,” says Rees. “There’s no predicted beaching and no closure for the family, the worst possible outcome. But we were able to show the family where we thought the body was and they had some comfort seeing that and knowing that the search had been modelled to the nth degree and all outcomes had been explored. It gave them some sort of closure.”

This is the main driver of Rees’ work, trying to find closure for these grieving families. He puts the modelling accuracy at around 66% as “good but with room for improvement”. The numerical modelling draws on the UK Met Office’s AMM15 model and pulls together a wide range of data sets, from river run off climatologies to bathymetry and substrate types, to residual transport patterns and pathways. In some cases, near-real-time data from satellites and footage from aircraft and drone flyovers add certainty to dynamic and fast-changing situations.

“The science is still in its infancy and we’re doing more research all the time,” says Rees, highlighting work underway to better understand the evolution of buoyancy of a missing person in the water, the succession of attrition by benthos – organisms – on a body trapped on the seabed (using pigs as analogues) and the increased use of data from metering and gauging stations on rivers. 

This is a fast-emerging area of oceanography, one delivering resource savings for police forces and perhaps, most importantly, providing some closure for those left behind when another soul is lost to the sea.

Amy McLellan is a freelance writer specialising in oil and gas who regularly contributes to Marine Professional and is the former editor of Energy Day and Frontier Energy. She is also a published author.