#01 2022

Extreme strokes against ocean plastic pollution

By Cristina Russo and Laura Braby, Physical Oceanographers, SAEON Egagasini Node

Plastic pollution has grown into one of the most devastating and overwhelming environmental issues facing us to date. The production of plastics is rising at such a rapid pace that it has overwhelmed the world and its ability to deal with it. Every year, approximately eight million tons of plastic ends up in our oceans, which, according to National Geographic, is the equivalent of 15 rubbish bags full of plastic covering every metre of coastline around the world. 

Raising awareness about ocean plastic pollution has never been more relevant than it is now. South African endurance swimmer and environmental activist, Sarah Ferguson, has decided to do exactly that by setting world records and simultaneously inspiring others to rethink plastic. As the founder of Breathe Conservation – an international non-profit organisation – she believes in a plastic-free ocean. Sarah wants to make the public aware of the ever-growing threat and devastating impact that plastic pollution is having on our oceans.

Sarah has pioneered a handful of extreme swims around the world, one of which has made her the first person to circumnavigate Easter Island – a swim of 60 km, 19 hours and 8 minutes. She is hoping to inspire people to make a difference, to help them appreciate that they can be part of the solution to plastic pollution, either through beach clean ups, refusing single-use plastic (yes, that means bringing your reusable coffee cup with you to work), or by making a conscious effort to recycle.

Figure 1. South African endurance swimmer and environmental activist, Sarah Ferguson, has pioneered a handful of extreme swims around the world (Photo courtesy of Wofty Wild)

Figure 2. Diagram illustrating the Agulhas Current and Sarah’s intended route for the swim. a) Typical Agulhas Current formation and b) Agulhas Current with an Agulhas Meander and a Durban Eddy, both of which can result in the occurrence of an inshore counter-current.

On 21 February of this year, Sarah took up her biggest challenge to date – to complete an approximately 1500-km-long stage swim along South Africa’s coastline, from Durban to Cape Town (Figure 2). To give some perspective, this is longer than the drive from Cape Town to Johannesburg.

The leg between Durban and East London is where Sarah aimed to break the world record for the fastest current-assisted, 100-km open-water swim. She hoped to achieve this in this region as it is home to one of the fastest-flowing currents in the world – the Agulhas Current.

While the Agulhas Current generally flows south-westward along South Africa’s east and south coasts, reaching maximum speeds of 1.5 m/s, there are times when the south-westward flow is directed offshore and replaced inshore by a north-eastward flowing counter-current, which has been observed to reach speeds of 0.8 m/s. This counter-current occurs in the presence of two types of cyclonic oceanic eddies known as Agulhas Meanders (Natal Pulses) or Durban Eddies (Figure 2b). These features, which are clockwise rotating columns of water with diameters as big as 200 km, travel downstream along the inshore edge of the Agulhas Current at varying speeds. However, they have at times been found to loiter in one particular area, resulting in an inshore counter-current that lasts somewhere between one and 30 days.

In addition to these ocean currents, Sarah anticipated several other obstacles along her swim which could include wind, waves, cold water temperatures, a variety of curious marine life as well as sea sickness!

Two physical oceanographers from SAEON’s Egagasini Node, Laura Braby and Cristina Russo, have helped orientate and prepare Sarah for the environment and dynamics of the Agulhas Current. In anticipation of Sarah’s swim, Laura and Cristina monitored the location of the Agulhas Current to determine whether or not one of these eddies may make an appearance. If they did, it could prove to make Sarah’s swim a bit more challenging than previously expected.

We commend Sarah in her journey toward making the ocean plastic-free.