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

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>