The researchers identified a total of 2,149 barrier islands worldwide using satellite images, topographical maps and navigational charts. The new total is significantly higher than the 1,492 islands identified in a 2001 survey conducted without the aid of publicly available satellite imagery.
All told, the 2,149 barrier islands measure 20,783 kilometers in length, are found along all continents except Antarctica and in all oceans, and make up roughly 10 percent of the Earth's continental shorelines. Seventy-four percent of the islands are found in the northern hemisphere.
Barrier islands help protect low-lying mainland coasts against erosion and storm damage, and can be important wildlife habitats. The nation with the most barrier islands is the United States, with 405, including those along the Alaskan Arctic shoreline.
The survey results appear in the current issue of the peer-reviewed Journal of Coastal Research.
"This provides proof that barrier islands exist in every climate and in every tide-wave combination," says Orrin H. Pilkey, James B. Duke Professor Emeritus of Geology at Duke's Nicholas School of the Environment. "We found that everywhere there is a flat piece of land next to the coast, a reasonable supply of sand, enough waves to move sand or sediment about, and a recent sea-level rise that caused a crooked shoreline, barrier islands exist."
Barrier islands often form as chains of long, low, narrow offshore deposits of sand and sediment, running parallel to a coast but separated from it by bays, estuaries or lagoons. Unlike stationary landforms, barrier islands build up, erode, migrate and rebuild over time in response to waves, tides, currents and other physical processes in the open ocean environment.
The 657 newly identified barrier islands didn't miraculously appear in the last decade, explains Matthew L. Stutz, assistant professor of geosciences at Meredith, located in Raleigh, N.C. They've long existed but were overlooked or misclassified in past surveys.
Previously, for instance, scientists believed barrier islands couldn't exist in locations with seasonal tides of more than four meters. Yet Stutz and Pilkey's survey identifies the world's longest chain of barrier islands along a stretch of the equatorial coast of Brazil, where spring tides reach seven meters.
The 54-island chain extends 571 kilometers along the fringe of a mangrove forest south of the mouth of the Amazon River. Past surveys didn't recognize it as a barrier island coast partly because older, low-resolution satellite images didn't show a clear separation between the islands and mangrove, Stutz says, but also because the chain didn't match the wave-tide criteria used to classify barrier islands in the United States, where most studies have been conducted. Scientists failed to consider that supplies of replenishing sand are so plentiful along the equatorial Brazilian coast that they can compensate for the erosion caused by higher spring tides.
Stutz and Pilkey say the survey's findings – which formed part of Stutz's dissertation when he was a doctoral student at Duke – illustrate the need for a new way to classify and study barrier islands, one that takes into account the complex interplay of local, regional and global variables that shape where the islands form and how they evolve.
"Are there clues there to predict which of today's islands might be in danger of disappearing in the near future?" Stutz asks.
The potential for significant climate and sea level change this century "underscores the need to improve our understanding of the fundamental roles these factors have played historically in island evolution, in order to help us better predict future impacts," Pilkey says.
"Barrier islands, especially in the temperate zone, are under tremendous development pressure, a rush to the oceanfront that ironically is timed to a period of rising sea levels and shoreline retreat," he says.
A developed barrier island, held in place by seawalls, jetties or groins, can't migrate. "It essentially becomes a sitting duck unable to respond to the changes occurring around it."
CITATION: "Open-Ocean Barrier Islands: Global Influence of Climatic, Oceanographic, and Depositional Settings," Matthew L. Stutz and Orrin H. Pilkey. Journal of Coastal Research: Volume 27, Issue 2: pp. 207 – 222. (2011) doi: 10.2112/09-1190.1
Tim Lucas | EurekAlert!
Colorado River's connection with the ocean was a punctuated affair
16.11.2017 | University of Oregon
Researchers create largest, longest multiphysics earthquake simulation to date
14.11.2017 | Gauss Centre for Supercomputing
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses