CAPE TOWN – An international study led out of the University of KwaZulu-Natal (UKZN) has used state-of-the-art techniques to investigate seabed sediments, revealing that severe tropical cyclones made landfall on the eastern coast of South Africa in the past and that under projected climate change conditions, these damaging phenomena could arise in the future.
Published in the journal, Nature Geoscience, the researchers used state-of-the-art techniques to investigate seabed sediments off the coast of Durban and found that there was a period – under higher sea levels – when storms were much more extreme than they are now.
While reconstructions of past storminess exist for the Atlantic and Pacific Oceans, the same cannot be said for much of the Indian Ocean, making this research important in filling a gap in knowledge to help understand what could happen under changing climate conditions and rising sea levels.
Head of the Marine Geology Research Unit at UKZN, Professor Andrew Green, led the research with honorary research Professor Andrew Cooper and Shannon Dixon from UKZN, Professor Matthias Zabel and Dr Annette Hahn from the University of Bremen’s Center for Marine Environmental Sciences in Germany, and Dr Carlos Loureiro from the University of Stirling in the UK.
“We found distinctive sediments that were deposited by severe storms that struck the coast between approximately five and seven thousand years ago,” said Green. “These storms were much bigger than any storm that happened in the 4 000 years since. This has allowed the storm sediments, or tempestites, to be preserved just beneath the seabed.”
The period of increased storminess coincided with warmer sea temperatures in the Indian Ocean and this allowed tropical storms to travel further south than they do presently.
Loureiro, lecturer in physical geography at the University of Stirling carried out modelling of the storm waves and analysed how current ocean trends and climate projections aligned with past climate conditions.
“This important work demonstrates that the past climate conditions that allowed very intense tropical cyclones to reach the South African coast are very similar to the ones projected now under climate change,” said Loureiro.
At present tropical storms are usually confined to central Mozambique but renewed ocean warming because of climate change could once again allow them to travel south, with potentially disastrous implications for cities like Maputo, Durban and Richard’s Bay.
“When these storms hit the coast there were no cities, buildings or roads and the coastline was free to adjust in a natural manner,” said Cooper.
“If such a storm were to happen now, beachfront infrastructure would be devastated and the rainfall associated with tropical cyclones would cause serious flooding.”
Cape Times