Joint press release – MARUM and ZMT
Over 100,000 years ago, boulders weighing many tons were washed onto a cliff in the Bahamas. It has been long debated whether the rocks were actually transported by ancient “super storms”. Dr. Alessio Rovere, along with scientific colleagues from MARUM – Center for Marine Environmental Sciences of the University of Bremen and from the Leibniz Centre for Tropical Marine Research (ZMT), have now discovered that storms with intensities that are not uncommon today combined with a few meters increase in sea level would be sufficient to achieve the feat. The journal Proceedings of the National Academy of Sciences published their results on October 30, 2017.
The boulders “cow” (left) and “bull” on the cliff at Eleuthera.
Photo: Alessio Rovere, MARUM and ZMT
Coastal regions worldwide are threatened by climate change and sea-level rise. Warmer climate conditions can increase the strength of storms and cause floods to occur more often – a growing hazard for the populations, the infrastructures and industries near the coasts.
It is therefore important to improve our predictions regarding the magnitude that extreme storms will increase in intensity and frequency in the future. For this, climate researchers rely on weather observations and model calculations, but also look beyond these into the past.
Super storms in the past
The last warm period, between around 128,000 and 116,000 years ago, is often used as a measure for comparison. This was the last period in Earth’s history during which the climate was warmer than in the pre-industrial era. Sea level was higher than it is today. It is thought that the North Atlantic was characterized at that time by “super storms”, which were stronger than any storms that have occurred since instruments have been used to record them.
On the east coasts of Bermuda and the Bahamas, various deposits that include giant boulders testify to erstwhile storm waves that engulfed the land. Dr. Alessio Rovere, leader of the Junior Research Group “Sea Level and Coastal Changes” at MARUM – Center for Marine Environmental Sciences of the University of Bremen and the Leibniz Centre for Tropical Marine Research (ZMT), has studied this in some detail together with his colleagues. “We wanted to know how much energy is required for a storm wave to move such huge boulders from the cliff edge to their present positions, and whether modern storms possess the energy to accomplish this feat.”
Storm waves transport boulders
On the Bahamian island of Eleuthera seven massive boulders are positioned atop a 15-meter-high cliff. According to a number of studies they were transported there by super storms. They are so gigantic that it is almost inconceivable that they could have been deposited there by waves. Two of the larger boulders are known in the region by the names “cow” and “bull”.
Rovere and his team have measured these two boulders, estimated their volumes and densities, and calculated a weight of 383 tons for the “cow” and 925 tons for the “bull”. The researchers fed the data collected on location into their computer model and adjusted for sea level at the time of deposition, which was up to 15 meters higher than today.
Using their wave model they simulated waves that were generated by three modern-era storms that hit Eleuthera especially hard: the “Perfect Storm” of 1991, Hurricane Andrew a year later, and Hurricane Sandy in 2012. The team of researchers carried out a scenario in the model where these storm waves strike the cliffs of Eleuthera, in order to calculate the wave height and length, as well as current speed, required to move the rocks.
Lessons for the future from waves in the distant past
“Our results indicate that a super storm was not necessary to explain the present positions of the two boulders,” says Rovere. “Even if we assume a sea level only six meters higher than that of today, waves such as those produced by Hurricane Sandy would have been sufficient to transport the boulders “cow” and “bull” to their present positions.” So for future storms it can be concluded that, even if the intensity of storms does not become greater, the rise of sea level alone would be enough to increase the frequency of strong waves during a storm as well as the current speed, which increases the wave energy.
Dr. Alessio Rovere
Telephone: 0421-218 65771
Giant boulders and Last Interglacial storm intensity in the North Atlantic
Alessio Rovere, Elisa Casella, Daniel L. Harris, Thomas Lorscheid, Napayalage A. K. Nandasena, Blake Dyer, Michael R. Sandstrom, Paolo Stocchi, William J. D’Andrea, Maureen E. Raymo
Lamont-Doherty Earth Observatory, Columbia University, USA
Leibniz Centre for Tropical Marine Research (ZMT), Bremen
MARUM – Center for Marine Environmental Sciences, University of Bremen
NIOZ Royal Netherlands Institute for Sea Research, The Netherlands
University of Auckland, New Zealand
University of Queensland, Australia
Further information – Photo material:
MARUM Public Relations
Telephone: 0421 218 65541
MARUM – Center for Marine Environmental Sciences of the University of Bremen, using state-of-the-art methods and through participation in international projects, investigates the role of the ocean in the Earth’s system, particularly with respect to global change. It quantifies the interactions between geological and biological processes in the ocean and contributes to the sustainable use of the oceans. MARUM comprises the DFG Research Centre and the Excellence Cluster “The Oceans in the Earth System.”
Leibniz Centre for Tropical Marine Research (ZMT)
Since 1991 the Leibniz Centre for Tropical Marine Research (ZMT) has dedicated its training and research to the better understanding of coastal ecosystems in the tropics. The ZMT focuses on the structure and functioning of these habitats, their response to anthropogenic and natural influences and the use of resources. In close cooperation with partners in the tropics, the ZMT leads interdisciplinary projects combining natural and social sciences. Scientists at the ZMT also support the development of expertise and structures in its partner countries to allow for sustainable coastal zone management.
Jana Stone | idw - Informationsdienst Wissenschaft
Live from the ocean research vessel Atlantis
13.12.2018 | National Science Foundation
NSF-supported scientists present new research results on Earth's critical zone
13.12.2018 | National Science Foundation
The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.
Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...
What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...
A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.
The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...
A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.
Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...
Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...
12.12.2018 | Event News
10.12.2018 | Event News
06.12.2018 | Event News
14.12.2018 | Power and Electrical Engineering
14.12.2018 | Physics and Astronomy
14.12.2018 | Physics and Astronomy