Developing Marine Robotics for the Western Indian Ocean - Needs, designs and applications

Overview

Abstract

The Western Indian Ocean (WIO) is one of the fastest warming parts of the global ocean. There is no doubt that this is due to Climate Change. Model projections indicate Sea Surface Temperature (SST) in the tropical WIO will rise some 5°C by 2100 with drastic destructive changes in the marine ecosystems and fisheries, impacting food security for the 60 M people who are dependent on this ocean. Inland droughts will accentuate this problem. By 2035 emergency food relief will be need in Mozambique, Kenya, Tanzania, Madagascar, Comoros, and Somalia (already happening). Emergency mitigation plans need to materialize as soon as possible. But these need to be designed around the scientific understanding of the situation. The problem is little is understood of the WIO and its marine ecosystems.

While much of the WIO ocean science can be done using models and satellites, in situ (observational) data are absolutely essential to calibrate these, especially the biology. Conventionally, this is done using research ships. But low-income WIO countries do not own these, and seldom do international vessels (owned by rich countries) venture into WIO. It is here that marine robotics can play an enormous role, but they can be difficult for WIO countries to afford. The Nelson Mandela University (NMU) has stepped up to the is need, with the aim to design and manufacture affordable ‘African’ engineered marine robots. Three prototypes have been manufactured — autonomous surface vehicle (Autoboat), an ocean glider, and an aerial drone.

Autonomous surface Vehicle (ASV)
This was designed to be inexpensive, lightweight, transport on top of a pick-up or small trailer, and only needs two people to deploy. Propulsion comes from two small battery-solar powered motors, allowing it to be deployed for months at sea, and has a large, encapsulated (waterproof) cargo and instrument bay. Survey-mode speed is 5 mph. Mobile phone or laptop software allows pre-determined surveyed grids and mission deployments. The ASB Mk I was demonstrated at the CLIVAR IORP/POGO Regional training workshop on observing the coastal and marginal seas in the western Indian Ocean (7-9 June 2022, in Mozambique; https://www.clivar.org/events/regional-training-workshop-observing-coastal-and-marginal-seas-western-indian-ocean). A Mark II is currently undergoing trials. The first research use of the Mk I will begin in 2023 by NMU postdoc Dr Sixolile Mazwane (see conference poster).

Ocean glider
The NMU ocean glider is intended to extend the surface sampling capability of the ASB with sub-surface data collection on the shelf region. As with other commercially available gliders (e.g., Slocum and Seaglider), it uses buoyancy changes to vertically profile the water column requiring very little onboard battery power. This gives it a long range. Upon each surfacing, it relays data via satellite to a shore base. Applications include academic, military, and commercial. Dimensions are 150 x 18 cm with a weight of 45 kg. Depth rating is 300 m, autonomy is 8-10 hrs, and navigation accuracy is +/- 2%. This version has completed phase 1 of trials.

Aerial coastal ocean drone
A strong need in WIO is to collect offshore in situ data quickly as deep ocean dynamics can change shelf processes in a matter of hours resulting in dramatic impacts on the productivity and biology. This is not possible using the ASB or glider which move slowly. Also, most shelves on the east coast of Africa are narrow and shallow (< 60 m) which means normal size foreign research vessels are too large to sample the shelf region. An aerial drone capable of traveling a distance of > 80 km, and able to hover to lower sampling probes into the water, is deemed an inexpensive, easy to use, alternative. The Mk I prototype has a payload of 80 kg. Once operational and proven, this version will be re-engineered to be more compact.
 

Biography

Prof Roberts holds a UK-SA Bilateral research Chair in Ocean Science & Marine Food Security between NMU and the University of Southampton. He has over 35 years working in this domain, and currently has a team comprising 65 scientists, postdocs and postgrad students spread between South Africa, the UK, France, Kenya, Mozambique, Tanzania and Madagascar. The focus of this research group is to understand current trends and predict future changes in the marine ecosystems in the Western Indian Ocean, and the impacts on the fisheries and people living in this region.