Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

What Will Climate Change and Sea Level Rise Mean for Barrier Islands?

16.06.2011
A new survey of barrier islands published earlier this spring offers the most thorough assessment to date of the thousands of small islands that hug the coasts of the world's landmasses.

The study, led by Matthew Stutz of Meredith College, Raleigh, N.C., and Orrin Pilkey of Duke University, Durham, N.C., offers new insight into how the islands form and evolve over time – and how they may fare as the climate changes and sea level rises.

The survey is based on a global collection of satellite images from Landsat 7 as well as information from topographic and navigational charts. The satellite images were captured in 2000, and processed by a private company as part of an effort funded by NASA and the U.S. Geological Survey.

During the 20th century, sea level has risen by an average of 1.7 millimeters (about 1/16 of an inch) per year. Since 1993, NASA satellites have observed an average sea level rise of 3.27 millimeters (about 1/8 of an inch) per year. A better understanding of how climate change and sea level rise are shaping barrier islands will also lead to a more complete grasp of how these dynamic forces are affecting more populated coastal areas.

Stutz, the study's lead author, highlighted a series of key findings from the new survey during an interview with a NASA science writer.

Every barrier island is unique.

Every island chain has a complex set of forces acting on it that underpin how islands form and how they're likely to change over time. Barrier islands often develop in the mouths of flooded river valleys as sea level rises, but they can also form at the end of rivers as sediment builds up and creates a delta. Other important factors in barrier island formation include regional tectonics, sea level changes, climate, vegetation and wave activity. "Understanding how such forces impact barrier islands is the key to understanding how climate change will affect our coastlines," noted Stutz.

Sea level rise can eliminate -- or create -- barrier islands.

Scientists estimate that the rate of sea level rise will likely double or triple in the next hundred years due to climate change. Paradoxically, gradual sea level rise can generate new barrier islands. Rising seas create shallow bays that develop barrier islands in the mouths of the bays along certain types of coastline.

Stutz's analysis found rising sea level in the last 5,000 years is associated with the greatest barrier island abundance, especially in the North Atlantic and Arctic. Stable or falling sea level, meanwhile, a pattern more typical of the Southern Hemisphere in the last 5,000 years, has produced fewer islands and a higher percentage of islands along river deltas.

However, extremely rapid sea level rise -- especially when coupled with decreases in sediment supply -- can simply inundate islands causing them to break up and disappear. Islands are eroding rapidly along the Mississippi Delta, Eastern Canada and the Arctic for these reasons.

"However, rising sea level is not just like pouring more water into a bathtub," Stutz emphasized. Islands react differently based on the geology in a region and how the waves and tides in an area are affected. People tend to assume sea level rise means fewer islands no matter what, but the rate of rise is critical."

There are far more barrier islands than previously thought.

A survey conducted by the same researchers tallied 1,492 barrier islands in 2001, but Stutz and Pilkey counted more than 2,149 this time. The difference: the researchers had access to higher-quality satellite imagery that covered a larger portion of the globe than they did last time. "It's not that 657 islands appeared overnight. We simply did a more thorough job of counting what was already out there," said Stutz. The researchers counted extensive island chains in Brazil, Madagascar and Australia that the previous survey had left out.

Barrier islands cluster along tectonically calm coasts.

Stable coasts, such as the eastern coast of the United States, tend to have wide, low relief areas with shallow estuaries that are conducive to barrier island formation. In contrast, continental margins near actively colliding plates, which generate earthquakes and volcanoes, produce fewer barrier islands. At active margins, such as the rocky cliffs along the Pacific, steep grades typically dominate coastal areas and prevent the formation of islands.

Northern and Southern hemisphere islands differ.

The Northern Hemisphere is home to the majority -- 74 percent -- of barrier islands. That's not surprising because the Northern Hemisphere contains about the same proportion of land. A less intuitive insight: the majority of Northern Hemisphere islands are in high-latitude Arctic or temperate climate zones, while most Southern Hemisphere islands are tropical. Why the discrepancy? Relative sea levels have fallen slowly in much of the Southern Hemisphere for the last 5,000 years, but the opposite has happened in the Arctic.

Storms are key molders of barrier island shape.

Storms tend to cause islands to retreat, carve new inlets that make them shorter and more numerous, and sometimes destroy them completely. The frequency of storms varies by latitude and climate. The Arctic and most temperate coasts experience regular storms, while more tropical areas experience few storms and more gentle swells most of the year, conditions that encourage the formation of sandy beaches. Major storms can cause drastic changes to barrier islands. After Hurricane Katrina, for example, many islands in the Mississippi River Delta were destroyed or radically changed.

Arctic barrier islands are retreating the fastest.

Barriers islands in the Arctic make up nearly a quarter of the world's barrier islands, and they're more vulnerable to climate change than islands anywhere else in the world. The reason: melting of sea ice and the permafrost that buffers Arctic islands from waves have left them susceptible to constant pounding from storms. Recently measured erosion rates in the Beaufort Sea show Arctic barrier islands eroding three to four times faster than islands in the continental United States. Any further acceleration in erosion rates could result in the rapid breakup of many Arctic islands, Stutz's analysis noted.

More research is needed, especially on a local scale.

Coastal areas will likely experience major changes in sea levels this century due to climate change. The shifts, however, will be anything but uniform. NASA research shows that some coasts are experiencing sea level rise significantly faster than the global average of 3.27 millimeters (about 1/8 of an inch) per year, while other areas are experiencing slower rates of rise and even falling sea levels. "It would be nice if we could say we can predict exactly how a given island or island chain will react to rising sea levels or some other environmental change, but we're simply not there yet for most islands, especially for many tropical islands where research dollars are scarce. We're still a long way from being able to accurately model how an individual island will change as a result of climate change or even simple development pressure," said Stutz.

Adam Voiland
NASA's Earth Science News Team

Adam Voiland | EurekAlert!
Further information:
http://www.nasa.gov
http://www.nasa.gov/topics/earth/features/barrier-islands.html

More articles from Earth Sciences:

nachricht Impacts of mass coral die-off on Indian Ocean reefs revealed
21.02.2017 | University of Exeter

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>