Tag: University of Southampton

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New Paper: New understanding of rip currents could help to save lives

ihaigh

This is a press-release for our new paper – Wave breaking patterns control rip current flow regimes and surf zone retention, which can be accessed here.

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Research by the Universities of Southampton and Plymouth has found a new link between breaking waves and the hazard posed by rip currents.

The research provides a better understanding why some surf zone conditions are more hazardous than others and could result in more lives being saved.

Researchers deploying GPS drifters

Researchers Dr Ivan Haigh (left) and Dr Cristos Mitsis deploying GPS drifters.

Hazardous rip currents are features on many beaches worldwide, and are thought to account for 68 per cent of rescue events involving the Royal National Lifeboat Institution’s beach lifeguards in the UK.

The study, which also involved researchers from Macquarie University (Sydney, AUS), and Deltares (Netherlands), used a combination of video imagery and in-situ rip current measurements at Perranporth Beach in Cornwall, which is well known for experiencing dangerous rips.

The researchers found that when waves break across the end of a rip channel, it in effect closes the channel and stops the currents from travelling far offshore. Crucially, however, they found that the absence of breaking waves across the channel promotes the formation of a much more hazardous rip current that can extend far offshore.

Sebastian Pitman, a PhD student in Ocean and Earth Science at the University of Southampton, who led the study, said: “For the first time, we combined images captured by cameras at the beach to detect wave breaking and GPS drifters to track the rip currents to better understand what drives rip dynamics. We used the images to identify whether the waves were breaking across the end of the rip channel, or not, and worked out what behaviour the GPS drifters in the rip current were exhibiting at those times.”

Perranporth Beach
Perranporth Beach – arrows show the location of rip current channels

Co-author Associate Professor Ivan Haigh, also of Ocean and Earth Science at the University of Southampton, said: “The combination of video imagery and GPS allowed us to identify that when wave breaking occurred across the rip channel, the rip current was often prevented from flowing far offshore. This would mean that anyone trapped in the current would be kept relatively close to the beach. However, when the waves ceased to break across the channel, we noticed that the rip currents would instead flow far offshore, presenting a much greater hazard to swimmers.”

This is the latest research into rip currents involving the University of Plymouth, with previous work having focussed on combining GPS drifter data with information recorded using current meters and water level sensors. This study builds on existing research between Plymouth and the RNLI and, for the first time, uses images captured at the beach to provide a comprehensive picture of the threats posed by rip currents.

Gerd Masselink, Professor of Coastal Geomorphology at the University of Plymouth, said: “It is possible to use the visually-observed wave breaking patterns to better understand why some surf zone conditions are more hazardous to bathers than others. This new information provides a useful means by which lifeguards on the beach can assess the hazard posed by a beach at a given time, which could result in more lives being saved.”

The findings are published in the Marine Geology journal, and are available here: http://www.sciencedirect.com/science/article/pii/S0025322716302821

Blog, coast, science, sea level

Back to the future to determine if sea level rise is accelerating

ihaigh

Here is the press release from my recent paper published in Nature Communications – ‘Time-scales for detecting a significant acceleration in sea level rise’.

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Scientists from Ocean and Earth Southampton and National Oceanography Centre Southampton have developed a new method for revealing how sea levels might rise around the world throughout the 21st century to address the controversial topic of whether the rate of sea level rise is currently increasing.

The international team of researchers, led by the University of Southampton and including scientists from the National Oceanography Centre, the University of Western Australia, the University of South Florida, the Australian National University and the University of Seigen in Germany, analysed data from 10 long-term sea level monitoring stations located around the world. They looked into the future to identify the timing at which sea level accelerations might first be recognised in a significant manner.

Lead author Dr Ivan Haigh, Lecturer in Coastal Oceanography at the University of Southampton, says: “Our results show that by 2020 to 2030, we could have some statistical certainty of what the sea level rise situation will look like for the end of the century. That means we’ll know what to expect and have 70 years to plan. In a subject that has so much uncertainty, this gives us the gift of long-term planning.

“As cities, including London, continue to plan for long-term solutions to sea level rise, we will be in a position to better predict the long-term situation for the UK capital and other coastal areas across the planet. Scientists should continue to update the analysis every 5 to 10 years, creating more certainty in long-term planning – and helping develop solutions for a changing planet.”

The study found that the most important approach to the earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual (occurring between years, or from one year to the next) to multidecadal (involving multiple decades) variability in sea level records.

“The measured sea levels reflect a variety of processes operating at different time scales,” says co-author Dr Francisco Calafat, from the National Oceanography Centre. He adds, “One of the main difficulties in detecting sea level accelerations is the presence of decadal and multi-decadal variations. For example, processes associated with the North Atlantic Oscillation have a strong influence on the sea levels around the UK over multi-decadal periods.  Such processes introduce a large amount of ‘noise’ into the record, masking any underlying acceleration in the rate of rise. Our study shows, that by adequately understanding these processes and removing their influence, we can detect accelerations much earlier.”

Co-author Professor Eelco Rohling, from the Australian National University and formerly of the University of Southampton, adds: “By developing a novel method that realistically approximates future sea level rise, we have been able to add new insight to the debate and show that there is substantial evidence for a significant recent acceleration in the sea level rise on a global and regional level. However, due to the large ‘noise’ signals at some local coastal sites, it won’t be until later this decade or early next decade before the accelerations in sea level are detection at these individual tide gauge sites.”

The findings of the study, funded by the Natural Environmental Research Council (iGlass consortium), are published in this months issue of the journal Nature Communications.

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Future flood losses in the world’s largest coastal cities

ihaigh

CLIMATE AND GEOHAZARDS

 

Over the next few decades climate change induced sea level rise and subsidence due to ground water pumping is expected to affect a greater proportion of people living in low lying  regions. Coupled with economic growth and increasing populations in coastal cities this trend will result in higher annual losses from flooding.

A recent Nature Climate Change article estimates that the average annual losses from flooding in the world’s largest coastal cities could rise from about $6 billion per year in 2005 to over $1 trillion per year by 2050. Even if investments are made to maintain flood probabilities at current levels, subsidence and sea level rise alone will increase annual losses to around $63 billion by 2050.

The above figure, from the article, shows the 20 cities where Average Annual Losses (AAL) increase the most (in relative terms in 2050 compared with 2005) if adaptive measures are taken…

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