In real estate, the cliché is “location, location, location”. When it comes to groundbreaking research on how the ocean and the atmosphere interact in the presence of human-created air pollution, and thus affect global climate change, that location is … South Africa.
This country – and Cape Town in particular – is the ideal place to do this research, for several reasons.
As one of the world’s largest coal-burning countries, South Africa contributes significantly to atmospheric pollution, in particular nitrogen emissions. This fuels two existential threats to this country and its people: poor air quality and climate change.
Of the top 20 causes of premature mortality in South Africa, nine (TB, respiratory infections, low birth weight, stroke, ischaemic heart disease, diabetes, heart disease, chronic obstructive pulmonary disease and asthma) are exacerbated by air pollution. And of the total number of deaths, roughly 20% are air pollution-related.
Previous research I have done assessed the impact of South African mortality related to fine particles, and found that the economic cost amounted to 4.5% of GDP. By comparison, the country’s agricultural sector contributes 2.5% of GDP.
Due to the relatively poorer quality of health, air pollution is even more damaging here than in a more developed country.
Regarding climate change, even if global warming is limited to 2℃, stronger and more frequent heatwaves will affect human health, crops and livestock, and tourism. We will have more severe droughts more often, and Cape Town’s narrowly missed “Day Zero” drought in 2018 will be five times more likely to occur.
Nitrogen pollution
Then there’s the bigger picture for our entire planet: how the nitrogen pollution we pump into the atmosphere upsets the global balance of things, and its impact on our oceans’ vital role as an enormous carbon sink.
We know the air pollution we create through activities such as fossil fuel combustion and agriculture, even hundreds of kilometres from the coast, is blown far out to sea, and then we’re not exactly sure what happens out there.
On the one hand, nitrogen actually assists the oceans in removing the greenhouse gas carbon dioxide (CO2) from the atmosphere. However, all this extra nitrogen can cause the production and release of nitrous oxide (N2O), another greenhouse gas that is 300 times as potent as CO2. But we have a poor idea of the processes taking place.
So we need to harness the scientific disciplines of atmospheric chemistry and oceanography, which until now have largely operated in isolation from each other, and find out. With the five-year, R7.5-million New Frontiers Research Award funding received from the Oppenheimer Memorial Trust, my team and I aim to do exactly that.
Unlike anywhere else on Earth, we have three diverse ocean systems, allowing for comparative study and measurement, within reach:
- The upwelling of nutrient-rich, cold waters from the deep ocean in the Benguela current up the west coast of Africa, teeming with phytoplankton that supports abundant marine life.
- The ocean desert of the South Atlantic Ocean, which is nutrient-poor and has limited marine life.
- The Southern Ocean, which boasts as close to the pre-industrial atmosphere as we can get anywhere on Earth – equivalent to the atmosphere up to 200 years ago.
Equally importantly, we have access to the polar research vessel, the R/V SA Agulhas II, allowing for research operations in these oceans. And we have the use of the University of Cape Town’s Marine Biogeochemistry Laboratory, the only such facility in Africa.
Our approach will focus on two main areas: data collection and novel modelling.
We will undertake an ambitious observational campaign to measure how much human-created atmospheric nitrogen deposition reaches the coastal and open ocean off the west coast of South Africa.
Regarding the impact of atmospheric nitrogen deposition on surface ocean biogeochemistry, we will conduct incubation experiments using atmospheric deposition collected on land and at sea.
Then, to investigate whether atmospheric deposition results in drawdown of CO2 and/or release of N2O from the surface ocean, we will conduct a set of model experiments.
First, an atmospheric chemistry model will generate fields of nitrogen deposition using current emissions as well as simulated increased anthropogenic emissions. Then those deposition fields will be used as inputs to an ocean biogeochemistry model, and the ocean’s response will be quantified.
This research requires a world-class, multidisciplinary team – combining ocean biogeochemistry, atmospheric chemistry modelling and high-resolution ocean modelling – and once again, South Africa is providing. That they’re all women is notable, but also coincidental: they happen to be the best in their fields. They are:
- Dr Sarah Fawcett, co-director of UCT’s Marine Biogeochemistry Laboratory, an ocean biogeochemist who specialises in nitrogen cycling as it pertains to marine productivity and climate.
- Professor Rebecca Garland, an atmospheric scientist in the University of Pretoria’s Department of Geography, Geoinformatics and Meteorology, where she leads the Laboratory for Atmospheric Sciences. For this project, she will employ a state-of-the-art model called Geos-Chem, to be used in South Africa for the first time.
- Dr Moagabo Ragoasha, a physical oceanographer and lecturer in UCT’s Department of Oceanography. Her research focuses on ocean dynamics and ocean-atmosphere interactions. In this project, Dr Ragoasha will apply her expertise in biogeochemical modelling to investigate how much nitrogen reaches the open ocean and its subsequent effects on marine ecosystems.
Supporting us will be postgraduate students and postdoctoral researchers, presenting an opportunity to nurture, in particular, black women oceanographers.
Together, we will establish a shared language and approach to the complex interactions between air pollution and our oceans – and find answers that not only benefit South Africa, but our entire planet. DM
Katye Altieri is associate professor of oceanography at the University of Cape Town and winner of the Oppenheimer Memorial Trust’s New Frontiers Research Award for 2025.